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Document and Entity Information - USD ($)	12 Months Ended
Dec. 31, 2017	Feb. 19, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	SUPERNUS PHARMACEUTICALS INC
Entity Central Index Key	0001356576
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,112,421,553
Entity Common Stock, Shares Outstanding		51,537,138
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 100,304	$ 66,398
Marketable securities	39,736	23,723
Accounts receivable, net	65,586	41,527
Inventories, net	16,304	16,801
Prepaid expenses and other current assets	6,521	2,955
Total current assets	228,451	151,404
Long term marketable securities	133,638	75,410
Property and equipment, net	5,124	4,344
Intangible assets, net	36,019	36,350
Other non-current assets	389	331
Deferred income taxes	20,843	41,729
Total assets	424,464	309,568
Current liabilities
Accounts payable	6,844	8,055
Accrued sales deductions	68,343	41,943
Accrued expenses	27,305	27,427
Income taxes payable	15,938	7
Non-recourse liability related to sale of future royalties, current portion	4,283	3,101
Deferred licensing revenue	287	209
Total current liabilities	123,000	80,742
Deferred licensing revenue, net of current portion	1,149	1,501
Convertible notes, net		4,165
Non-recourse liability related to sale of future royalties, long term	22,258	27,289
Other non-current liabilities	10,577	4,002
Derivative liabilities		114
Total liabilities	156,984	117,813
Stockholders' equity
Common stock, $0.001 par value, 130,000,000 shares authorized at December 31, 2017 and December 31, 2016; 51,314,850 and 49,971,267 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	51	50
Additional paid-in capital	294,999	276,127
Accumulated other comprehensive loss, net of tax	(747)	(134)
Accumulated deficit	(26,823)	(84,288)
Total stockholders' equity	267,480	191,755
Total liabilities and stockholders' equity	$ 424,464	$ 309,568

Consolidated Statements of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Net product sales	$ 294,097	$ 210,078	$ 143,526
Royalty revenue	6,367	4,686	3,038
Licensing revenue	1,774	239	901
Total revenue	302,238	215,003	147,465
Costs and expenses
Cost of product sales	15,215	11,986	8,423
Research and development	49,577	42,791	29,135
Selling, general and administrative	137,905	106,010	89,063
Total costs and expenses	202,697	160,787	126,621
Operating earnings	99,541	54,216	20,844
Other income (expense)
Interest income	2,864	1,467	681
Interest expense	(134)	(543)	(1,229)
Interest expense-nonrecourse liability related to sale of future royalties	(1,434)	(4,548)	(3,541)
Changes in fair value of derivative liabilities	76	448	193
Loss on extinguishment of debt	(295)	(671)	(2,338)
Total other income (expense)	1,077	(3,847)	(6,234)
Earnings before income taxes	100,618	50,369	14,610
Income tax expense (benefit)	43,334	(40,852)	666
Net earnings	$ 57,284	$ 91,221	$ 13,944
Earnings per share
Basic (in dollars per share)	$ 1.13	$ 1.84	$ 0.29
Diluted (in dollars per share)	$ 1.08	$ 1.76	$ 0.28
Weighted-average number of common shares outstanding
Basic (in shares)	50,756,603	49,472,434	47,485,258
Diluted (in shares)	53,301,150	51,708,983	51,160,380

Consolidated Statements of Changes in Stockholder's Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2014	$ 43	$ 230,263	$ (154)	$ (189,453)	$ 40,699
Beginning balance (in shares) at Dec. 31, 2014	42,974,463
Increase (Decrease) in Stockholders' Equity
Share-based compensation		4,090			4,090
Issuance of employee stock purchase plan shares		930			930
Issuance of employee stock purchase plan shares (in shares)	98,986
Exercise of stock options		937			937
Exercise of stock options (in shares)	205,640
Equity issued on conversion of convertible notes	$ 6	27,083			27,089
Equity issued on conversion of convertible notes (in shares)	5,693,062
Exercise of warrants		652			652
Exercise of warrants (in shares)	32,523
Net earnings				13,944	13,944
Other comprehensive loss			(334)		(334)
Unrealized (loss) gain on marketable securities, net of tax					(334)
Ending balance at Dec. 31, 2015	$ 49	263,955	(488)	(175,509)	88,007
Ending balance (in shares) at Dec. 31, 2015	49,004,674
Increase (Decrease) in Stockholders' Equity
Share-based compensation		5,926			5,926
Issuance of employee stock purchase plan shares		1,494			1,494
Issuance of employee stock purchase plan shares (in shares)	109,244
Exercise of stock options		557			557
Exercise of stock options (in shares)	85,694
Equity issued on conversion of convertible notes	$ 1	4,161			4,162
Equity issued on conversion of convertible notes (in shares)	771,655
Net earnings				91,221	91,221
Other comprehensive loss					354
Unrealized (loss) gain on marketable securities, net of tax			354		354
Other		34			34
Ending balance at Dec. 31, 2016	$ 50	276,127	(134)	(84,288)	191,755
Ending balance (in shares) at Dec. 31, 2016	49,971,267
Increase (Decrease) in Stockholders' Equity
Cumulative-effect of adoption of ASU 2016-09		211		181	392
Adjusted Balance	$ 50	276,338	(134)	(84,107)	192,147
Share-based compensation		8,433			8,433
Issuance of employee stock purchase plan shares		1,888			1,888
Issuance of employee stock purchase plan shares (in shares)	71,256
Exercise of stock options		3,793			3,793
Exercise of stock options (in shares)	407,477
Equity issued on conversion of convertible notes	$ 1	4,547			4,548
Equity issued on conversion of convertible notes (in shares)	864,850
Net earnings				57,284	57,284
Other comprehensive loss					(613)
Unrealized (loss) gain on marketable securities, net of tax			(613)		(613)
Ending balance at Dec. 31, 2017	$ 51	$ 294,999	$ (747)	$ (26,823)	$ 267,480
Ending balance (in shares) at Dec. 31, 2017	51,314,850

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net earnings	$ 57,284	$ 91,221	$ 13,944
Adjustments to reconcile net earnings to net cash provided by operating activities:
Loss on extinguishment of debt	295	671	2,338
Change in fair value of derivative liability	(76)	(448)	(193)
Depreciation and amortization	8,132	2,399	921
Amortization of deferred financing costs and debt discount	50	278	687
Amortization of premium/discount on marketable securities	(563)	242	61
Non-cash interest expense on non-recourse liability related to sale of future royalties	1,434	4,548	3,541
Non-cash royalty revenue	(5,283)	(4,686)	(3,038)
Share-based compensation expense	8,433	5,926	4,090
Deferred income tax provision	21,224	(41,787)
Changes in operating assets and liabilities:
Accounts receivable	(24,059)	(15,619)	(8,638)
Inventories	497	(4,214)	854
Prepaid expenses and other current assets	(3,566)	2,306	(1,582)
Accounts payable	(620)	3,470	2,061
Accrued sales deductions	26,400	15,149	18,333
Accrued expenses	2,888	7,539	507
Income taxes payable	15,931	7
Deferred licensing revenue	(274)	144	149
Other non-current liabilities	6,513	(334)	489
Net cash provided by operating activities	114,640	66,812	34,524
Cash flows from investing activities
Purchases of marketable securities	(101,889)	(47,364)	(63,859)
Sales and maturities of marketable securities	28,657	31,824	37,581
Purchases of property, plant and equipment	(2,029)	(1,603)	(2,104)
Deferred legal fees	(11,154)	(18,821)	(10,907)
Net cash used in investing activities	(86,415)	(35,964)	(39,289)
Cash flows from financing activities
Proceeds from issuance of common stock	5,681	2,052	1,867
Net cash provided by financing activities	5,681	2,052	1,867
Net change in cash and cash equivalents	33,906	32,900	(2,898)
Cash and cash equivalents at beginning of year	66,398	33,498	36,396
Cash and cash equivalents at end of year	100,304	66,398	33,498
Supplemental cash flow information:
Cash paid for interest	134	493	825
Income taxes paid	1,588
Noncash financial activity:
Conversion of convertible notes and interest make-whole	4,548	4,162	27,089
Exercise of warrants			652
Deferred legal fees included in accounts payable and accrued expenses	521	$ 5,122	$ 9,789
Unsettled purchase of marketable securities included in accrued expenses	$ 1,004

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company's consolidated financial statements include the accounts of Supernus Pharmaceuticals, Inc. and Supernus Europe Ltd., collectively referred to herein as "Supernus" or "the Company." All significant intercompany transactions and balances have been eliminated in consolidation. The Company's consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the U.S. (U.S. GAAP).

The Company, which is primarily located in the U.S., operates in one operating segment.

Use of Estimates

The preparation of the financial statements in accordance with U.S. GAAP requires the Company to make estimates and judgments in certain circumstances that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. In preparing these consolidated financial statements, management has made its best estimates and judgments of certain amounts included in the financial statements, giving due consideration to materiality. On an ongoing basis, the Company evaluates its estimates, including those related to revenue recognition, future royalty revenue related to Orenitram net product sales, accrued sales deductions, fair value of financial assets and liabilities, derivative liabilities, common stock options, income taxes, preclinical study and clinical trial accruals, and other contingencies. Management bases its estimates on historical experience or on various forecasts, including information received from its service providers, which it has assessed to be reasonable under the circumstances. Actual results could differ from these estimates.

Cash and Cash Equivalents

The Company considers all investments in highly liquid financial instruments with an original maturity of three months or less to be cash equivalents.

Marketable Securities

Marketable securities consist of investments in U.S. Treasury bills and notes, certificates of deposit, various U.S. governmental agency debt securities, corporate and municipal bonds and other fixed income securities. The Company places all investments with government, industrial, or financial institutions whose debt is rated as investment grade. The Company classifies all available-for-sale marketable securities with maturities greater than one year from the balance sheet date as non-current assets.

The Company's investments are classified as available-for-sale and are carried at estimated fair value. Any unrealized holding gains or losses are reported, net of any reported tax effects, as accumulated other comprehensive earnings (loss), which is a separate component of stockholders' equity.

Realized gains and losses, and declines in value judged to be other-than-temporary, if any, are included in consolidated results of operations. A decline in the market value of any available-for-sale security below cost that is deemed to be other-than-temporary results in a reduction in fair value, with that reduction charged to earnings in that period. A new cost basis for the security is then established. Dividend and interest income is recognized when earned. The cost of securities sold is calculated using the specific identification method.

The Company established the Supernus Supplemental Executive Retirement Plan (SERP) for the sole purpose of receiving funds for executives from a previous SERP and providing a continuing deferral program under the Supernus SERP. As of December 31, 2017 and 2016, the estimated fair value of the mutual fund investment securities within the SERP was approximately $335,000 and $275,000, respectively. The fair value of these assets is included within other non-current assets on the consolidated balance sheets. A corresponding noncurrent liability is also included in the consolidated balance sheets to reflect the Company's obligation for the SERP. The Company has not made, and has no plans to make, contributions to the SERP. The securities are restricted in nature and can only be used for purposes of paying benefits under the SERP.

Accounts Receivable, Net

Accounts receivable are reported on the consolidated balance sheets at outstanding amounts, less an allowance for doubtful accounts and discounts. The Company extends credit without requiring collateral. The Company writes off uncollectible receivables when the likelihood of collection is remote. The Company evaluates the collectability of accounts receivable on a regular basis, but no less frequently than quarterly. An allowance, when needed, is based upon various factors, including the financial condition and payment history of customers, an overall review of collections experience on other accounts, and economic factors or events expected to affect future collections experience.

The Company recorded no allowance for bad debt in 2017 and approximately $42,000 allowance for bad debts as of December 31, 2016. No accounts were written off in 2017 and 2016.

The Company recorded an allowance of approximately $8.9 million and $5.6 million for expected sales discounts as of December 31, 2017 and December 31, 2016, respectively.

The following table includes those customers, who are wholesalers and distributors, that represent more than 10% of total net product sales for 2017 and more than 10% of the accounts receivable balance on the consolidated balance sheet as of December 31, 2017:

	Percent of Net Product Sales			Percent of Accounts Receivable, net
Customer A		30	%		46	%
Customer B		30	%		22	%
Customer C		37	%		28	%

		97	%		96	%

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents, accounts receivable and marketable securities. The counterparties are various corporations and financial institutions of high credit standing.

Substantially all of the Company's cash and cash equivalents are maintained with U.S. government agencies and well known corporations. Deposits held with banks may exceed the amount of insurance provided on such deposits. Generally, these deposits may be redeemed upon demand and, therefore, management believes they bear minimal default risk.

Inventories

Inventories, which are recorded at the lower of cost or market, include materials, labor, and other direct and indirect costs and are valued using the first-in, first-out method. The Company capitalizes inventories produced in preparation for commercial launches when it becomes probable that the related product candidates will receive regulatory approval and that the related costs will be recoverable through the commercial sale of the product.

Property and Equipment

Property and equipment are stated at cost. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to operations. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are computed using the straight-line method over the following useful lives:

Computer equipment		3 years
Software		3 years
Lab equipment and furniture		5 - 10 years
Leasehold improvements		Shorter of lease term or useful life

Intangible Assets

Intangible assets consist of patent defense costs, which are deferred legal fees that have been incurred in connection with legal proceedings related to the defense of patents for Oxtellar XR and Trokendi XR. Patent defense costs will be charged to expense in the event of an unsuccessful outcome of the ongoing litigation. Patents are carried at cost less accumulated amortization, which is calculated on a straight-line basis over the estimated useful lives of the patents. Amortization commences in the quarter after the costs are incurred. The amortization period is based initially upon the remaining patent life and is adjusted, if necessary, for any subsequent settlements or other changes to the expected useful life of the patent. The carrying value of the patents is assessed for impairment annually during the fourth quarter of each year, or more frequently if impairment indicators exist. There were no indicators of impairment identified at December 31, 2017.

Impairment of Long-Lived Assets

Long-lived assets consist primarily of property and equipment and patent defense costs. The Company assesses the recoverability of its long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If indications of impairment exist, projected future undiscounted cash flows associated with the asset are compared to the carrying value to determine whether the asset's value is recoverable. Evaluating for impairment requires judgment, including the estimation of future cash flows, future growth rates and profitability, and the expected life over which cash flows will occur. Changes in the Company's business strategy or adverse changes in market conditions could impact impairment analyses and require the recognition of an impairment charge equal to the excess of the carrying value of the long-lived asset over its estimated fair value. There were no indicators of impairment identified for the Company's long-lived assets as of December 31, 2017.

Deferred Financing Costs

Deferred financing costs consist of financing costs incurred by the Company in connection with the issuance of the Company's 7.50% Convertible Senior Secured Notes (see Note 8). The Company amortized deferred financing costs over the term of the related debt using the effective interest method. All related deferred financing costs have been written off, coincident with the conversion of all remaining Notes in 2017. The was no remaining balance at December 31, 2017.

Preclinical Study and Clinical Trial Accruals

The Company estimates preclinical study and clinical trial expenses based on the services performed pursuant to contracts with research institutions, clinical investigators, and clinical research organizations (CROs) that conduct activities on our behalf. In recording service fees, the Company estimates the time period over which the related services will be performed and compares the level of effort expended through the end of each period to the cumulative expenses recorded and payments made for such services. As appropriate, it accrues additional service fees or defers any non-refundable advance payments until the related services are performed. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust its accrued expenses or deferred advance payments accordingly. If the Company later determines that it no longer expects the services associated with a nonrefundable advance payment to be rendered, the advance payment will be charged to expense in the period in which such determination is made.

Revenue from Product Sales

Revenue from product sales is recognized when: persuasive evidence of an arrangement exists; delivery has occurred and title to the product and associated risk of loss has passed to the customer; the price is fixed or determinable; collection from the customer has been reasonably assured; all performance obligations have been met; and returns and allowances can be reasonably estimated. Product sales are recorded net of estimated rebates, chargebacks, allowances, discounts, patient copay assistance and other deductions as well as estimated product returns (collectively, "sales deductions").

Our products are distributed through wholesalers and pharmaceutical distributors. Each of these wholesalers and distributors takes title and ownership to the product upon physical receipt of the product and then distributes our products to pharmacies.

Sales Deductions

Allowances for estimated sales deductions are provided for the following:


	•	Rebates. Rebates include mandated discounts under the Medicaid Drug Rebate Program, the Medicare coverage gap program, as well as negotiated discounts with commercial healthcare providers. Rebates are amounts owed after the final dispensing of product to a benefit plan participant has occurred and are based upon contractual agreements or legal requirements with the public sector (e.g., Medicaid) and with private sector benefit providers (e.g., commercial managed care providers). The allowance for rebates is based on statutory and contractual discount rates and anticipated rebates based on a plan provider's utilization. Rebates are generally invoiced and paid quarterly in arrears so that the accrual balance consists of an estimate of the amount expected to be incurred for the current quarter's activity, plus an accrual balance for known or estimated prior quarters' unpaid rebates. If actual rebates vary from estimates, we may need to adjust balances of such rebates to reflect the actual expenditures of the Company with respect to these programs, thereby affecting revenue in the period of adjustment.
	•	Co-pay assistance. Patients who pay in cash or have commercial insurance and meet certain eligibility requirements may receive co-pay assistance from the Company. The intent of this program is to reduce the patient's out of pocket costs. Liabilities for co-pay assistance are based on actual program participation and estimates of program redemption using data provided by third-party administrators.
	•	Distributor/Wholesaler Deductions and Discounts. U.S. specialty distributors and wholesalers are offered various forms of consideration including allowances, service fees and prompt payment discounts as consideration for distributing our products. Distributor allowances and service fees arise from contractual agreements with distributors and are generally a percentage of the price at which the Company sells product to distributors and wholesalers. Wholesale customers are offered a prompt pay discount for payment within a specified period.
	•	Returns. Sales of our products are not subject to a general right of return; however, the Company will accept product that is damaged or defective when shipped directly from our warehouse. The Company will accept expired product six months prior to and up to 12 months subsequent to its expiry date. Product that has been used to fill patient prescriptions is no longer subject to any right of return.
	•	Chargebacks. Chargebacks are discounts that occur when contracted customers purchase directly from an intermediary distributor or wholesaler. Contracted customers, which currently consist primarily of Public Health Service institutions and federal government entities purchasing via the Federal Supply Schedule, generally purchase our product at a discounted price. The distributor or wholesaler, in turn, charges back the difference between the price initially paid by the distributor or wholesaler and the discounted price paid to the distributor or wholesaler by the customer. The allowance for distributor/wholesaler chargebacks is based on sales to contracted customers.

Revenue Recognition of License Revenue

License and Collaboration Agreements

We have entered into collaboration agreements to have both Oxtellar XR and Trokendi XR commercialized outside of the U.S. These agreements generally include an up-front license fee and ongoing milestone payments upon the achievement of specific events. We believe that when milestones meet all of the necessary criteria to be considered substantive, these should be recognized as revenue when achieved. For up-front license fees, we have estimated the service period of the contract and are recognizing this revenue on a straight-line basis over the respective service period.

Milestone Payments

Milestone payments on licensing agreements are recognized as revenue when the collaborative partner acknowledges completion of the milestone and substantive effort was necessary to achieve the milestone. Management may recognize revenue contingent upon the achievement of a milestone in its entirety in the period in which the milestone is achieved only if the milestone meets all the criteria to be considered substantive. Substantive milestone payments are recognized upon achievement of the milestone only if all of the following conditions are met:


	•	The milestone payments are non-refundable;
	•	Achievement of the milestone involves a degree of risk and was not reasonably assured at the inception of the arrangement;
	•	Substantive effort on the partner's part is involved in achieving the milestone; and
	•	The amount of the milestone payment is reasonable in relation to the effort expended or the risk associated with achievement of the milestone.

Determination as to whether a payment meets the aforementioned conditions involves management's judgment. If any of these conditions are not met, the resulting payment would not be considered a substantive milestone, and therefore the resulting payment would be considered part of the consideration for the single unit of accounting and amortized over the appropriate period.

The Company recorded $1.5 million of milestone revenue during the year ended December 31, 2017. There was no milestone revenue during the year ended December 31, 2016 and $0.8 million of milestone revenue for the year ended December 31, 2015.

Royalty Revenue

We recognize non-cash royalty revenue for royalty amounts earned pursuant to a royalty agreement with United Therapeutics. In 2014, the Company sold certain of these royalty rights to Healthcare Royalty Partners III, L.P. (HC Royalty) (see Note 15). Accordingly, the Company records non-cash royalty revenue when payments are made from United Therapeutics to HC Royalty in connection with these agreements. Royalty revenue also includes royalty amounts received from collaboration partners, including Shire Pharmaceuticals Inc., based on net product sales of Mydayis.

Cost of Product Sales

The cost of product sales consists primarily of materials, third-party manufacturing costs, freight and distribution costs, allocation of labor, quality control and assurance, and other manufacturing overhead costs.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs consist primarily of: employee-related expenses, including salaries and benefits; share-based compensation expense; expenses incurred under agreements with CROs; fees paid to clinical investigators who are participating in our clinical trials; fees paid to consultants and other vendors that conduct the Company's clinical trials; the cost of acquiring and manufacturing clinical trial materials; the cost of manufacturing materials used in process validation, but only to the extent that those materials are manufactured prior to receiving regulatory approval and are not expected to be sold commercially; facilities costs that do not have an alternative future use; related depreciation and other allocated expenses; license fees for, and milestone payments related to in-licensed products and technologies; and costs associated with animal testing activities and regulatory approvals.

Advertising Expense

The costs of the Company's advertising efforts are expensed as incurred. The Company incurred approximately $33.8 million, $21.9 million and $19.3 million in advertising costs for the years ended December 31, 2017, 2016 and 2015, respectively. These expenses are recorded in the selling, general and administrative expense line item.

Share-Based Compensation

Employee share-based compensation is measured based on the estimated fair value as of the grant date. The grant date fair value is calculated using the Black-Scholes option-pricing model, which requires the use of subjective assumptions including stock volatility, expected term, risk-free rate, and the fair value of the underlying common stock. The Company recognizes expense using the straight-line method.

The Company records the expense for stock option grants to non-employees based on the estimated fair value of the stock option using the Black-Scholes option pricing model. The fair value of non-employee awards is re-measured at each reporting period. As a result, stock compensation expense for non-employee awards with vesting is affected by subsequent changes in the fair value of the Company's common stock, with those changes recorded in the relevant period.

Income Taxes

The Company utilizes the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using tax rates and laws that are expected to be in effect when the differences are expected to reverse. When appropriate, valuation allowances are established to reduce deferred tax assets to the amounts expected to be realized.

The Company accounts for uncertain tax positions in its consolidated financial statements when it is more-likely-than-not that the position will be sustained upon examination by the tax authorities. Such tax positions must initially and subsequently be measured as the largest amount of tax benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the tax authority, assuming full knowledge of the position and relevant facts. The Company's policy is to recognize any interest and penalties related to income taxes as income tax expense.

Recently Issued Accounting Pronouncements

Accounting Pronouncements Adopted in 2017

In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, "Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting." The standard is intended to simplify several areas of accounting for share-based compensation arrangements, including the income tax impact, classification on the statement of cash flows and forfeitures. ASU 2016-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016, and early adoption is permitted. The Company adopted ASU 2016-09 on January 1, 2017 using the modified retrospective approach. As a result, the Company recorded a cumulative effect adjustment of $211,000 to increase the 2017 beginning of period additional paid-in capital balance, with an offset to accumulated deficit for historical forfeiture assumptions. Additionally, the Company recorded an opening balance sheet adjustment of $392,000 to increase its deferred tax asset, with an offset to accumulated deficit, primarily to recognize excess tax benefits (i.e. windfalls) from stock option exercises in prior years and the impact of the $211,000 adjustment to historical forfeiture expense.

New Accounting Pronouncements Not Yet Adopted

In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers," and has subsequently issued a number of amendments to ASU 2014-09. The new standard, as amended, provides a comprehensive model to be used in the accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific guidance. The standard's stated core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, ASU 2014-09 includes provisions with a five step model that includes identifying the contract with a customer, identifying the performance obligations in the contract, determining the transaction price, allocating the transaction price to performance obligations, and recognizing revenue when, or as, an entity satisfies a performance obligation. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers.

The new standard will be effective for the Company beginning January 1, 2018 and permits two methods of adoption: the full retrospective method, which requires the standard to be applied to each prior period presented, or the modified retrospective method, which requires the cumulative effect of adoption to be recognized as an adjustment to opening retained earnings in the period of adoption. The Company will adopt the standard using the modified retrospective method on January 1, 2018.

We have completed an analysis of existing contracts with our customers and assessed the differences in accounting for such contracts under ASU 2014-09 compared with current revenue accounting standards. Based on our review of current customer contracts, we do not expect the implementation of ASU 2014-09 to have a material quantitative impact on our consolidated financial statements as the timing of revenue recognition for product sales is not expected to significantly change. Under the new standard, we expect the timing of revenue recognition for upfront licensing fees from our license and collaboration agreements and royalty arrangements to be accelerated. In addition, royalties from sales of licensed products will be recognized as the underlying sales of product occur by the licensee. The Company has substantially completed its impact assessment and expects the cumulative effect adjustment to retained earnings on January 1, 2018, reflecting the acceleration of revenue recognition, is not material. The adoption of the new standard will also result in additional revenue-related disclosures in the footnotes to our consolidated financial statements. The Company continues to evaluate the impact of the new guidance on its financial statement disclosures.

In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)." The standard requires a lessee to recognize assets and liabilities on the balance sheet for leases with lease terms greater than 12 months. ASU 2016-02 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. We expect the ASU to have a material impact on our assets and liabilities due to the addition of previously classified operating leases, but we do not expect it to have a material impact on our cash flows or results of operations.

In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities." ASU 2017-12 provides new guidance about income statement classification and eliminates the requirement to separately measure and report hedge ineffectiveness. The entire change in fair value for qualifying hedge instruments included in the effectiveness measurement will be recorded in other comprehensive income (OCI) and amounts deferred in OCI will be reclassified to earnings in the same income statement line item in which the earnings effect of the hedged item is reported. This standard will be effective for the first annual period beginning after December 15, 2018, including interim periods within those periods. Early adoption is permitted. The Company is currently assessing the impact that this standard will have on its consolidated financial statements, but does not expect it to have a material impact.

In May 2017, the FASB issued ASU 2017-09, "Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting," which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. ASU 2017-09 is effective for all annual periods, and interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements.

In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments." The standard eliminates diversity in the practice of how certain cash receipts and cash payments are presented and classified in the statement of cash flows under Topic 230, Statement of Cash Flows, and other Topics. ASU 2016-15 is effective for annual reporting periods, and interim periods therein, beginning after December 15, 2017. The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements.

The Company has evaluated all other ASUs issued through the date the consolidated financials were issued in this Annual Report on Form 10-K and believes that no other ASU will have a material impact on the Company's consolidated financial statements.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2017

Fair Value of Financial Instruments

Fair Value of Financial Instruments

3. Fair Value of Financial Instruments

The fair value of an asset or liability should represent the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Such transactions to sell an asset or transfer a liability are assumed to occur in the principal or most advantageous market for the asset or liability. Accordingly, fair value is determined based on a hypothetical transaction at the measurement date, considered from the perspective of a market participant rather than from a reporting entity's perspective.

The Company reports assets and liabilities that are measured at fair value using a three level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows:


	•	Level 1—Inputs are unadjusted quoted prices in active markets for identical assets that the Company has the ability to access at the measurement date.
	•	Level 2—Inputs are quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (interest rates, yield curves, etc.) and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).
	•	Level 3—Unobservable inputs that reflect the Company's own assumptions, based on the best information available, including the Company's own data.

In accordance with the fair value hierarchy described above, the following tables show the fair value of the Company's financial assets and liabilities that are required to be measured at fair value, in thousands of dollars:

	Fair Value Measurements at December 31, 2017
	Total Carrying Value at December 31, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	100,304	$	100,304	$	—	$	—
Marketable securities		39,736		2,118		37,618		—
Corporate debt securities		132,477		448		132,029
Government debt securities		1,161		—		1,161
Marketable securities—restricted (SERP)		335		—		335		—

Total assets at fair value	$	274,013	$	102,870	$	171,143	$	—

	Fair Value Measurements at December 31, 2016
	Total Carrying Value at December 31, 2016		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	66,398	$	66,398	$	—	$	—
Marketable securities		23,723		656		23,067		—
Corporate debt securities		74,343		1,717		72,626
Government debt securities		1,067				1,067
Marketable securities—restricted (SERP)		275		—		275		—

Total assets at fair value	$	165,806	$	68,771	$	97,035	$	—


Liabilities:
Derivative liabilities	$	114	$	—	$	—	$	114

The fair value of the restricted marketable securities is included within other non-current assets in the consolidated balance sheets.

The Company's Level 1 assets include cash held with banks, certificates of deposit, and money market funds.

Level 2 assets include the SERP (Supplemental Executive Retirement Plan) assets, commercial paper and investment grade corporate and government debt securities and other fixed income securities. Level 2 securities are valued using third-party pricing sources that apply applicable inputs and other relevant data in their models to estimate fair value.

Level 3 liabilities include the estimated fair value of the interest make-whole liability associated with the Company's Notes, which are recorded as derivative liabilities. The "make-whole fundamental change" provision (as defined in the Indenture governing the Notes) expired on May 1, 2017.

The carrying amounts of other financial instruments, including accounts receivable, accounts payable and accrued expenses approximate fair value due to their short-term maturities.

Unrestricted marketable securities held by the Company were as follows, in thousands of dollars:

At December 31, 2017:

Available for Sale		Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Fair Value
Corporate and government debt securities		$	174,235			48			(909	)	$	173,374

At December 31, 2016:

Available for Sale		Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Fair Value
Corporate and government debt securities		$	99,487			86			(440	)	$	99,133

The contractual maturities of the unrestricted available for sale marketable securities held by the Company were as follows, in thousands of dollars:

	December 31, 2017
Less Than 1 Year	$	39,736
1 year to 2 years		42,921
2 year to 3 years		43,021
3 years to 4 years		47,696
Greater Than 4 Years		—

Total	$	173,374

The Company has not experienced any other-than-temporary losses on its marketable securities and restricted marketable securities. The cost of securities sold is calculated using the specific identification method.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Share-Based Payments

12 Months Ended

Dec. 31, 2017

Share-Based Payments

Share-Based Payments

10. Share-Based Payments

Stock Option Plans

The Company has adopted the Supernus Pharmaceuticals, Inc. 2012 Equity Incentive Plan (the 2012 Plan), which is stockholder approved, and provides for the grant of stock options and certain other awards, including stock appreciation rights (SAR), restricted and unrestricted stock, stock units, performance awards, cash awards and other awards that are convertible into or otherwise based on the Company's common stock, to the Company's key employees, directors, consultants and advisors. The 2012 Plan is administered by the Company's Board of Directors and the Company's Compensation Committee and provides for the issuance of up to 8,000,000 shares of the Company's Common Stock. Option awards are granted with an exercise price equal to the estimated fair value of the Company's Common Stock at the grant date. Option awards granted to employees, consultants and advisors generally vest in four annual installments, starting on the first anniversary of the date of the grant and have ten-year contractual terms. Option awards granted to the directors generally vest over a one year term and have ten-year contractual terms.

Share-based compensation recognized related to the grant of employee and non-employee stock options, SAR, Employee Stock Purchase Plan (ESPP) awards and non-vested stock was as follows, in thousands of dollars:

	Year Ended December 31,
	2017		2016		2015
Research and development	$	1,387	$	1,107	$	874
Selling, general and administrative		7,046		4,819		3,216

Total	$	8,433	$	5,926	$	4,090

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model and the assumptions in the following table:

	Year Ended December 31,
	2017	2016	2015
Fair value of common stock	$25.30 - $41.00	$12.98 - $22.80	$9.13 - $21.21
Expected volatility	53.61% - 60.6%	60.9% - 64.5%	60.9% - 64.6%
Dividend yield	0%	0%	0%
Expected term	6.25 years	6.25 years	6.25 years
Risk-free interest rate	1.90% - 2.18%	1.14% - 2.15%	1.54% - 1.74%
Expected forfeiture rate	0%	5%	5%

Fair Value of Common Stock—The fair value of the Common Stock underlying the option grants was determined based on observable market prices of the Company's Common Stock.

Expected Volatility—Volatility is a measure of the amount by which a financial variable such as a share price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. The Company has identified several public entities of similar size, complexity, and stage of development. Accordingly, historical volatility has been calculated using the volatility of these companies, as well as taking into consideration the Company's actual volatility since our IPO. As our historical experience is not sufficient to calculate volatility for our option grants, the Company will continue to use the guideline peer group volatility information until the historical volatility of its own Common Stock is sufficient on its own to measure expected volatility for future option grants.

Dividend Yield—The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Expected Term—This is the period of time that the options granted are expected to remain unexercised. Options granted have a maximum term of ten years. The Company determines the average expected life of stock options according to the "simplified method" as described in Staff Accounting Bulletin 110, which is the mid-point between the vesting date and the end of the contractual term. Over time, management will track estimates of the expected life of the option term so that estimates will approximate actual experience for similar options.

Risk-Free Interest Rate—This is the U.S. Treasury note rate during the week each option grant was issued during the year, with a term that most closely resembles the expected term of the option.

Expected Forfeiture Rate—Prior to 2017, the forfeiture rate was the estimated percentage of options granted that are anticipated to be forfeited or canceled on an annual basis before becoming fully vested. Under ASU 2016-09, adopted January 1, 2017, the forfeiture rate is zero. The Company accounts for forfeitures as they occur.

The following table summarizes stock option and SAR activity:

	Number of Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)
Outstanding, December 31, 2015		2,699,007		$	8.94		7.92
Granted		1,058,850		$	13.32
Exercised		(85,694	)	$	6.51
Forfeited		(28,075	)	$	12.23

Outstanding, December 31, 2016		3,644,088		$	10.25		7.59
Granted		1,130,155		$	26.57
Exercised		(407,477	)	$	9.31
Forfeited		(86,096	)	$	17.24

Outstanding, December 31, 2017		4,280,670		$	14.50		7.37


As of December 31, 2017:
Vested and expected to vest		4,280,670		$	14.50		7.37
Exercisable		1,952,769		$	9.35		6.16

As of December 31, the aggregate intrinsic value of options outstanding is $108.5 million, $54.7 million, and $12.6 million for 2017, 2016, and 2015, respectively. As of December 31, the aggregate intrinsic value of options vested and expected to vest is $108.5 million, $54.0 million, and $12.4 million, for 2017, 2016, and 2015, respectively. As of December 31, the aggregate intrinsic value of options which are exercisable is $59.6 million, $25.0 million, and $5.0 million, for 2017, 2016, and 2015, respectively.

The weighted-average, grant-date, fair value of options which were granted for the years ended December 31, 2017, 2016 and 2015 was $14.35, $7.66 and $6.05 per share, respectively.

The total fair value of the underlying Common Stock related to shares that vested during the years ended December 31, 2017, 2016 and 2015 was approximately $5.4 million, $3.9 million and $2.6 million, respectively.

The total intrinsic value of options exercised amounted to approximately $12.8 million, $1.1 million and $1.6 million, respectively, during the years ended December 31, 2017, 2016 and 2015.

As of December 31, 2017 and 2016, the total unrecognized compensation expense was approximately $17.6 million and $9.8 million, respectively, which the Company expects to recognize over a weighted-average period of 2.8 and 2.7 years, respectively.

Earnings per Share

12 Months Ended

Dec. 31, 2017

Earnings per Share

Earnings per Share

11. Earnings per Share

Basic earnings per common share is determined by dividing earnings attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted earnings per share is computed by dividing the earnings attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company's stock option grants, SAR, and potential ESPP awards, and the if-converted method is used to determine the dilutive effect of the Company's Notes.

The following Common Stock equivalents were excluded in the calculation of diluted earnings per share because their inclusion would be anti-dilutive as applied to the earnings from continuing operations applicable to common stockholders for the years ended December 31, 2017, 2016 and 2015:

	Year Ended December 31,
	2017		2016		2015
Warrants to purchase common stock		—		—		20,957
Stock options, stock appreciation rights, and ESPP awards		40,009		22,944		25,027

The following table sets forth the computation of basic and diluted net earnings per share for the years ended December 31, 2017, 2016 and 2015, in thousands of dollars, except share and per share amounts:

	Year Ended December 31,
	2017			2016			2015
Numerator, in thousands:
Net earnings used for calculation of basic EPS	$	57,284		$	91,221		$	13,944
Interest expense on convertible debt		134			543			1,229
Changes in fair value of derivative liabilities		(76	)		(448	)		(589	)
Loss on extinguishment of debt		295			671			2,338
Loss on extinguishment of outstanding debt,
as if converted		(321	)		(1,182	)		(2,494	)

Total adjustments		32			(416	)		484

Net earnings used for calculation of diluted EPS	$	57,316		$	90,805		$	14,428


Denominator:
Weighted average shares outstanding, basic		50,756,603			49,472,434			47,485,258
Effect of dilutive potential common shares:
Shares underlying Convertible Senior Secured Notes		285,257			1,222,363			2,459,009
Shares issuable to settle interest make-whole derivatives		7,012			71,537			804,507
Stock options and stock appreciation rights		2,252,278			942,649			411,606

Total potential dilutive common shares		2,544,547			2,236,549			3,675,122

Weighted average shares outstanding, diluted		53,301,150			51,708,983			51,160,380


Net earings per share, basic	$	1.13		$	1.84		$	0.29
Net earnings per share, diluted	$	1.08		$	1.76		$	0.28

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

Income Taxes

12. Income Taxes

On December 22, 2017, the U.S. enacted the Tax Cuts and Jobs Act (Tax Act), resulting in significant modifications to existing law. The Tax Act, among other things, lowered the U.S. corporate income tax rate from 35 percent to 21 percent effective January 1, 2018. The Tax Act also enhanced and extended through 2026 the option to claim accelerated depreciation on qualified property and expanded limitations on the deductibility of executive compensation.

The Company recognized the income tax effects of the Tax Act in accordance with Staff Accounting Bulletin No. 118, which provides guidance for the application of ASC Topic 740, Income Taxes, in the reporting period in which the Tax Act was signed into law. The Company's financial results in 2017 reflect the income tax effects of the Tax Act for which the accounting under ASC Topic 740 is provisional for those specific income tax effects of the Tax Act for which the accounting under ASC Topic 740 is incomplete but a reasonable estimate could be determined. The Company did not identify items for which the income tax effects of the Tax Act have not been completed and a reasonable estimate could not be determined as of December 31, 2017.

The changes to existing U.S. tax laws as a result of the Tax Act that have most significant impact to the Company's federal income taxes is the reduction of the U.S. corporate income tax rate. The Company's deferred tax assets and liabilities were remeasured to reflect the reduction in the U.S. corporate income tax rate from 35 percent to 21 percent. The Company wrote down its net deferred tax assets as of December 31, 2017 by $9.7 million to reflect the estimated impact of the decrease in federal statutory rates on the value of its net deferred tax asset and recorded a corresponding net one-time income tax expense of $9.7 million, all of which was non-cash. Additionally, the provisional amount recognized by the Company in 2017 attributable to the accelerated depreciation on qualified property is not material. Based on analysis by the Company, the impact on the deductibility of executive compensation as it relates to the stock compensation is also not material.

The Company had substantially completed its analysis of the income tax effects of the Tax Act and does not anticipate material adjustments to the recorded amounts, however, the final results could vary from these recorded amounts. The net one-time charge related to the effects of the Tax Act may differ due to, among other things, further refinements of our calculations, changes in interpretations and assumptions that that Company has made, and related accounting policy decisions that the Company may take as a result of the Tax Act. Additionally potential further guidance, regulations, interpretations and rulings may be forthcoming from accounting and regulatory bodies and federal and state tax agencies, which could result in additional impacts. The Company will complete its analysis over a one-year measurement period ending December 22, 2018 and any adjustments during this measurement period will be included in net earnings from continuing operations as adjustment to income tax expense in the reporting period in which such adjustments are determined.

The components of the income tax (benefit)/ expense for the years ended December 31, 2017, 2016 and 2015 were as follow, in thousands of dollars:

	Year Ended December 31,
	2017			2016			2015
Current
Federal	$	18,288		$	544		$	624
State		3,822			78			42
Deferred
Federal		21,493			(39,898	)		—
State		(269	)		(1,576	)		—

Total	$	43,334		$	(40,852	)	$	666

A reconciliation of the expected income tax (benefit)/ expense computed using the U.S. Federal statutory income tax rate to the Company's effective income tax rate is as follows, in thousands of dollars:

	Year Ended December 31,
	2017			2016			2015
Income tax expense computed at U.S. Federal statutory tax rate	$	35,217		$	17,629		$	5,114
Permanent items		(2,311	)		715			601
State income taxes		2,714			(1,523	)		42
Change in valuation allowance		—			(56,019	)		(4,705	)
Uncertain income tax position		(1,137	)		143			533
Research and development credits		(2,196	)		(1,902	)		(979	)
Other		1,353			105			60
Deferred rate change		9,694			—			—

Income tax expense/ (benefit)	$	43,334		$	(40,852	)	$	666

The significant components of the Company's deferred income tax assets (liabilities) were as follow, in thousands of dollars:

	As of December 31,
	2017			2016
Deferred tax assets:
Net operating loss carryforward	$	5,072		$	24,926
Deferred rent credit		211			417
Accrued compensation and non-qualified stock options		7,090			8,128
Deferred financing costs		—			128
Depreciation and amortization		2,073			706
Research and development credits		3,795			7,119
Capitalized overhead into inventory (UNICAP §263A)		480			1,086
Nonrecourse liability related to sale of future royalties		6,377			11,223
Other		645			878
AMT credit		1,613			1,581
Accrued sales deductions		8,449			—

Net deferred tax asset		35,805			56,192
Deferred tax liability:
Debt discount on convertible notes		—			(141	)
Infringement legal cost		(10,557	)		(13,899	)
Depreciation		(264	)		(423	)
Section 481(a)		(4,141	)		—

Net deferred taxes	$	20,843		$	41,729

In assessing the realizability of deferred income tax assets, management considers whether it is more-likely-than-not that some or all of the deferred income tax assets will not be realized. The ultimate realization of the deferred income tax assets is dependent upon the generation of future taxable income during the periods in which the net operating loss (NOL) and tax credit carryforwards are available. Management considers projected future taxable income, the scheduled reversal of deferred income tax liabilities, and available tax planning strategies that can be implemented by the Company in making this assessment. Based upon the level of historical taxable income and projections for future taxable income over the periods in which the NOL and credit carryforwards are available to reduce income taxes payable, management had determined it is more-likely-than-not to realize such net deferred tax assets.

As of December 31, 2017, the U.S. Federal and state NOL carryforwards amounted to approximately $32.1 million ($6.7 million tax effected) and $8.1 million ($0.5 million tax effected), respectively, and will expire in various years beginning in 2030. As of December 31, 2017, the Company has available research and development credit carryforwards of approximately $4.2 million, which expire, if unused, starting in 2026. The use of the Company's U.S. Federal and State NOL carryforwards and research and development credits are restricted in annual use due to changes in the Company's ownership. For the year ended December 31, 2017, the Company utilized NOLs of approximately $51.0 million and expects the remaining $32.1 million of Federal NOL carryforwards to become available over the years from 2018 to 2020, in amounts ranging from $7.1 million to $18.4 million per year. In addition, the Company has available research and development credits of approximately $4.2 million, expected to become available in 2019 to 2020. The Company's state NOLs will have a similar limitation to the amount noted for the U.S. Federal NOLs. Additionally, despite the NOL carryforwards, the Company may have a future tax liability due to state and local income tax requirements. The Company paid no Federal income taxes in the years ended December 31, 2016 or 2015.

The Company accounts for uncertain income tax positions pursuant to the guidance in FASB ASC Topic 740, Income Taxes. The Company recognizes interest and penalties related to uncertain tax positions, if any, in income tax expense. As of December 31, 2017, the Company accrued interest of a nominal amount and penalties of $0.1 million related to uncertain tax positions. The Company's income taxes have not been subject to examination by any tax jurisdictions since its inception in 2005. Due to NOL and research and development credit carryforwards, all U.S. Federal and state income tax returns filed by the Company are subject to examination by the taxing jurisdictions. Some uncertain income tax position liabilities have been recorded against the Company's deferred income tax assets to offset such tax attribute carryforwards and other positions that can't be offset by tax attributes until a liability has been booked.

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows, in thousands of dollars:

	Year Ended December 31,
	2017			2016			2015
Balance as of January 1	$	9,299		$	9,341		$	8,964
Gross increases (decreases) related to prior-year tax positions		947			—			(5	)
Gross increases related to current-year tax positions		1,178			662			646
Gross decreases related to prior-year tax positions		—			(375	)		—
Gross decreases related to current-year tax positions		—			(169	)		(243	)
Change in tax rates		(2,565	)		(160	)		(21	)

Balance as of December 31	$	8,859		$	9,299		$	9,341

As of December 31, 2017 and 2016, the Company recorded zero and $0.5 million of current tax expense on setting up an uncertain tax position related to the Alternative Minimum Tax. The Company also recorded a $0.4 million expense on setting up an uncertain tax position related to state tax nexus. The Company does not anticipate a significant increase or decrease in the uncertain income tax benefits within the next 12 months.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies

Basis of Presentation

The Company, which is primarily located in the U.S., operates in one operating segment.

Use of Estimates

Cash and Cash Equivalents

The Company considers all investments in highly liquid financial instruments with an original maturity of three months or less to be cash equivalents.

Marketable Securities

Accounts Receivable, Net

The Company recorded no allowance for bad debt in 2017 and approximately $42,000 allowance for bad debts as of December 31, 2016. No accounts were written off in 2017 and 2016.

The Company recorded an allowance of approximately $8.9 million and $5.6 million for expected sales discounts as of December 31, 2017 and December 31, 2016, respectively.

	Percent of Net Product Sales			Percent of Accounts Receivable, net
Customer A		30	%		46	%
Customer B		30	%		22	%
Customer C		37	%		28	%

		97	%		96	%

Concentration of Credit Risk

Inventories

Property and Equipment

Computer equipment		3 years
Software		3 years
Lab equipment and furniture		5 - 10 years
Leasehold improvements		Shorter of lease term or useful life

Intangible Assets

Impairment of Long-Lived Assets

Deferred Financing Costs

Preclinical Study and Clinical Trial Accruals

Revenue from Product Sales

Sales Deductions

Allowances for estimated sales deductions are provided for the following:


	•	Rebates. Rebates include mandated discounts under the Medicaid Drug Rebate Program, the Medicare coverage gap program, as well as negotiated discounts with commercial healthcare providers. Rebates are amounts owed after the final dispensing of product to a benefit plan participant has occurred and are based upon contractual agreements or legal requirements with the public sector (e.g., Medicaid) and with private sector benefit providers (e.g., commercial managed care providers). The allowance for rebates is based on statutory and contractual discount rates and anticipated rebates based on a plan provider's utilization. Rebates are generally invoiced and paid quarterly in arrears so that the accrual balance consists of an estimate of the amount expected to be incurred for the current quarter's activity, plus an accrual balance for known or estimated prior quarters' unpaid rebates. If actual rebates vary from estimates, we may need to adjust balances of such rebates to reflect the actual expenditures of the Company with respect to these programs, thereby affecting revenue in the period of adjustment.
	•	Co-pay assistance. Patients who pay in cash or have commercial insurance and meet certain eligibility requirements may receive co-pay assistance from the Company. The intent of this program is to reduce the patient's out of pocket costs. Liabilities for co-pay assistance are based on actual program participation and estimates of program redemption using data provided by third-party administrators.
	•	Distributor/Wholesaler Deductions and Discounts. U.S. specialty distributors and wholesalers are offered various forms of consideration including allowances, service fees and prompt payment discounts as consideration for distributing our products. Distributor allowances and service fees arise from contractual agreements with distributors and are generally a percentage of the price at which the Company sells product to distributors and wholesalers. Wholesale customers are offered a prompt pay discount for payment within a specified period.
	•	Returns. Sales of our products are not subject to a general right of return; however, the Company will accept product that is damaged or defective when shipped directly from our warehouse. The Company will accept expired product six months prior to and up to 12 months subsequent to its expiry date. Product that has been used to fill patient prescriptions is no longer subject to any right of return.
	•	Chargebacks. Chargebacks are discounts that occur when contracted customers purchase directly from an intermediary distributor or wholesaler. Contracted customers, which currently consist primarily of Public Health Service institutions and federal government entities purchasing via the Federal Supply Schedule, generally purchase our product at a discounted price. The distributor or wholesaler, in turn, charges back the difference between the price initially paid by the distributor or wholesaler and the discounted price paid to the distributor or wholesaler by the customer. The allowance for distributor/wholesaler chargebacks is based on sales to contracted customers.

Revenue Recognition of License Revenue

License and Collaboration Agreements

Milestone Payments


	•	The milestone payments are non-refundable;
	•	Achievement of the milestone involves a degree of risk and was not reasonably assured at the inception of the arrangement;
	•	Substantive effort on the partner's part is involved in achieving the milestone; and
	•	The amount of the milestone payment is reasonable in relation to the effort expended or the risk associated with achievement of the milestone.

Royalty Revenue

Cost of Product Sales

Research and Development Costs

Advertising Expense

Share-Based Compensation

Income Taxes

Recently Issued Accounting Pronouncements

Accounting Pronouncements Adopted in 2017

New Accounting Pronouncements Not Yet Adopted

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value of Financial Instruments

Schedule of fair value of the financial assets and liabilities

	Fair Value Measurements at December 31, 2017
	Total Carrying Value at December 31, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	100,304	$	100,304	$	—	$	—
Marketable securities		39,736		2,118		37,618		—
Corporate debt securities		132,477		448		132,029
Government debt securities		1,161		—		1,161
Marketable securities—restricted (SERP)		335		—		335		—

Total assets at fair value	$	274,013	$	102,870	$	171,143	$	—

	Fair Value Measurements at December 31, 2016
	Total Carrying Value at December 31, 2016		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	66,398	$	66,398	$	—	$	—
Marketable securities		23,723		656		23,067		—
Corporate debt securities		74,343		1,717		72,626
Government debt securities		1,067				1,067
Marketable securities—restricted (SERP)		275		—		275		—

Total assets at fair value	$	165,806	$	68,771	$	97,035	$	—


Liabilities:
Derivative liabilities	$	114	$	—	$	—	$	114

Schedule of unrestricted marketable securities

Unrestricted marketable securities held by the Company were as follows, in thousands of dollars:

At December 31, 2017:

Available for Sale		Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Fair Value
Corporate and government debt securities		$	174,235			48			(909	)	$	173,374

At December 31, 2016:

Available for Sale		Amortized Cost			Gross Unrealized Gains			Gross Unrealized Losses			Fair Value
Corporate and government debt securities		$	99,487			86			(440	)	$	99,133

Schedule of contractual maturities of the unrestricted available for sale marketable securities held

The contractual maturities of the unrestricted available for sale marketable securities held by the Company were as follows, in thousands of dollars:

	December 31, 2017
Less Than 1 Year	$	39,736
1 year to 2 years		42,921
2 year to 3 years		43,021
3 years to 4 years		47,696
Greater Than 4 Years		—

Total	$	173,374

Share-Based Payments (Tables)

12 Months Ended

Dec. 31, 2017

Share-Based Payments

Schedule of share-based compensation recognized related to the grant of employee and non-employee stock options, SAR, Employee Stock Purchase Plan (ESPP) awards and non-vested stock

	Year Ended December 31,
	2017		2016		2015
Research and development	$	1,387	$	1,107	$	874
Selling, general and administrative		7,046		4,819		3,216

Total	$	8,433	$	5,926	$	4,090

Schedule of assumptions used in estimation of fair value of each award option on the date of grant using Black-Scholes option-pricing model

	Year Ended December 31,
	2017	2016	2015
Fair value of common stock	$25.30 - $41.00	$12.98 - $22.80	$9.13 - $21.21
Expected volatility	53.61% - 60.6%	60.9% - 64.5%	60.9% - 64.6%
Dividend yield	0%	0%	0%
Expected term	6.25 years	6.25 years	6.25 years
Risk-free interest rate	1.90% - 2.18%	1.14% - 2.15%	1.54% - 1.74%
Expected forfeiture rate	0%	5%	5%

Summary of stock option and SAR activity

	Number of Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)
Outstanding, December 31, 2015		2,699,007		$	8.94		7.92
Granted		1,058,850		$	13.32
Exercised		(85,694	)	$	6.51
Forfeited		(28,075	)	$	12.23

Outstanding, December 31, 2016		3,644,088		$	10.25		7.59
Granted		1,130,155		$	26.57
Exercised		(407,477	)	$	9.31
Forfeited		(86,096	)	$	17.24

Outstanding, December 31, 2017		4,280,670		$	14.50		7.37


As of December 31, 2017:
Vested and expected to vest		4,280,670		$	14.50		7.37
Exercisable		1,952,769		$	9.35		6.16

Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings per Share

Schedule of common stock equivalents excluded in the calculation of diluted income per share

	Year Ended December 31,
	2017		2016		2015
Warrants to purchase common stock		—		—		20,957
Stock options, stock appreciation rights, and ESPP awards		40,009		22,944		25,027

Schedule of computation of basic and diluted net income per share

	Year Ended December 31,
	2017			2016			2015
Numerator, in thousands:
Net earnings used for calculation of basic EPS	$	57,284		$	91,221		$	13,944
Interest expense on convertible debt		134			543			1,229
Changes in fair value of derivative liabilities		(76	)		(448	)		(589	)
Loss on extinguishment of debt		295			671			2,338
Loss on extinguishment of outstanding debt,
as if converted		(321	)		(1,182	)		(2,494	)

Total adjustments		32			(416	)		484

Net earnings used for calculation of diluted EPS	$	57,316		$	90,805		$	14,428


Denominator:
Weighted average shares outstanding, basic		50,756,603			49,472,434			47,485,258
Effect of dilutive potential common shares:
Shares underlying Convertible Senior Secured Notes		285,257			1,222,363			2,459,009
Shares issuable to settle interest make-whole derivatives		7,012			71,537			804,507
Stock options and stock appreciation rights		2,252,278			942,649			411,606

Total potential dilutive common shares		2,544,547			2,236,549			3,675,122

Weighted average shares outstanding, diluted		53,301,150			51,708,983			51,160,380


Net earings per share, basic	$	1.13		$	1.84		$	0.29
Net earnings per share, diluted	$	1.08		$	1.76		$	0.28

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of components of the income tax (benefit)/ expense

The components of the income tax (benefit)/ expense for the years ended December 31, 2017, 2016 and 2015 were as follow, in thousands of dollars:

	Year Ended December 31,
	2017			2016			2015
Current
Federal	$	18,288		$	544		$	624
State		3,822			78			42
Deferred
Federal		21,493			(39,898	)		—
State		(269	)		(1,576	)		—

Total	$	43,334		$	(40,852	)	$	666

Schedule of reconciliation of the expected income tax (benefit)/ expense computed using the federal statutory income tax rate to the entity's effective income tax rate

	Year Ended December 31,
	2017			2016			2015
Income tax expense computed at U.S. Federal statutory tax rate	$	35,217		$	17,629		$	5,114
Permanent items		(2,311	)		715			601
State income taxes		2,714			(1,523	)		42
Change in valuation allowance		—			(56,019	)		(4,705	)
Uncertain income tax position		(1,137	)		143			533
Research and development credits		(2,196	)		(1,902	)		(979	)
Other		1,353			105			60
Deferred rate change		9,694			—			—

Income tax expense/ (benefit)	$	43,334		$	(40,852	)	$	666

Schedule of Significant components of the entity's deferred tax assets (liabilities)

The significant components of the Company's deferred income tax assets (liabilities) were as follow, in thousands of dollars:

	As of December 31,
	2017			2016
Deferred tax assets:
Net operating loss carryforward	$	5,072		$	24,926
Deferred rent credit		211			417
Accrued compensation and non-qualified stock options		7,090			8,128
Deferred financing costs		—			128
Depreciation and amortization		2,073			706
Research and development credits		3,795			7,119
Capitalized overhead into inventory (UNICAP §263A)		480			1,086
Nonrecourse liability related to sale of future royalties		6,377			11,223
Other		645			878
AMT credit		1,613			1,581
Accrued sales deductions		8,449			—

Net deferred tax asset		35,805			56,192
Deferred tax liability:
Debt discount on convertible notes		—			(141	)
Infringement legal cost		(10,557	)		(13,899	)
Depreciation		(264	)		(423	)
Section 481(a)		(4,141	)		—

Net deferred taxes	$	20,843		$	41,729

Schedule of reconciliation of the beginning and ending amount of gross unrecognized tax benefits

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows, in thousands of dollars:

	Year Ended December 31,
	2017			2016			2015
Balance as of January 1	$	9,299		$	9,341		$	8,964
Gross increases (decreases) related to prior-year tax positions		947			—			(5	)
Gross increases related to current-year tax positions		1,178			662			646
Gross decreases related to prior-year tax positions		—			(375	)		—
Gross decreases related to current-year tax positions		—			(169	)		(243	)
Change in tax rates		(2,565	)		(160	)		(21	)

Balance as of December 31	$	8,859		$	9,299		$	9,341

Convertible Senior Secured Notes (Details) - USD ($)		12 Months Ended				44 Months Ended	50 Months Ended
Convertible Senior Secured Notes (Details) - USD ($)	May 03, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2016	Dec. 31, 2017
Details of Notes reflected in balance sheet
Accretion of debt discount and deferred financing costs		$ 50,000	$ 278,000	$ 687,000
Remaining outstanding balance			4,165,000			$ 4,165,000
Loss on extinguishment of debt		$ 295,000	671,000	$ 2,338,000
7.50% Convertible Senior Secured Notes due 2019
Notes payable
Amount issued	$ 90,000,000
Interest rate (as a percent)	7.50%	7.50%					7.50%
Conversion rate for the Notes (in shares)					188.7059
Conversion ratio, principal amount		$ 1,000					$ 1,000
Conversion price, per share of Common Stock		$ 5.30					$ 5.30
Offering expenses	$ 3,500,000
Unamortized debt issuance costs	2,600,000
Details of Notes reflected in balance sheet
Gross proceeds						90,000,000
Initial value of interest make-whole derivative reported as debt discount						(9,270,000)
Conversion option reported as debt discount and APIC	$ 900,000					(22,336,000)
Conversion of debt to equity - principal		$ (4,575,000)	(3,900,000)			(85,425,000)	$ (90,000,000)
Conversion of debt to equity - accretion of debt discount and deferred financing costs		360,000	25,767,000			25,767,000	360,000
Accretion of debt discount and deferred financing costs		50,000				5,429,000
Remaining outstanding balance		$ 0	$ 4,165,000			$ 4,165,000	$ 0
Shares of common stock issued in conversion of Notes		900,000	700,000				17,000,000
Shares of common stock issued in settlement of the interest make-whole provision			24,000				2,200,000
Loss on extinguishment of debt		$ 300,000	$ 700,000

Share-Based Payments - Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assumptions used in estimating the fair value of each option award using the Black-Scholes option-pricing model
Expected forfeiture rate (as a percent)	0.00%
Stock option and Stock Appreciation Rights
Number of Options and SAR
Outstanding at the beginning of the period (in shares)	3,644,088	2,699,007
Granted (in shares)	1,130,155	1,058,850
Exercised (in shares)	(407,477)	(85,694)
Forfeited (in shares)	(86,096)	(28,075)
Outstanding at the end of the period (in shares)	4,280,670	3,644,088	2,699,007
Vested and expected to vest (in shares)	4,280,670
Exercisable (in shares)	1,952,769
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 10.25	$ 8.94
Granted (in dollars per share)	26.57	13.32
Exercised (in dollars per share)	9.31	6.51
Forfeited (in dollars per share)	17.24	12.23
Outstanding at the end of the period (in dollars per share)	14.50	$ 10.25	$ 8.94
Vested and expected to vest (in dollars per share)	14.50
Exercisable (in dollars per share)	$ 9.35
Stock Option
Assumptions used in estimating the fair value of each option award using the Black-Scholes option-pricing model
Expected volatility, minimum (as a percent)	53.61%	60.90%	60.90%
Expected volatility, maximum (as a percent)	60.60%	64.50%	64.60%
Dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected term	6 years 3 months	6 years 3 months	6 years 3 months
Risk-free interest rate, minimum (as a percent)	1.90%	1.14%	1.54%
Risk-free interest rate, maximum (as a percent)	2.18%	2.15%	1.74%
Expected forfeiture rate (as a percent)	0.00%	5.00%	5.00%
Weighted-Average Remaining Contractual Term (in years)
Outstanding at the end of the period	7 years 4 months 13 days	7 years 7 months 2 days	7 years 11 months 1 day
Vested and expected to vest	7 years 4 months 13 days
Exercisable	6 years 1 month 28 days
Share-based payments, additional disclosure
Aggregate intrinsic value of options outstanding	$ 108.5	$ 54.7	$ 12.6
Aggregate intrinsic value of options vested and expected to vest	108.5	54.0	12.4
Aggregate intrinsic value of options exercisable	$ 59.6	$ 25.0	$ 5.0
Weighted-average, grant-date fair value of options granted (in dollars per share)	$ 14.35	$ 7.66	$ 6.05
Total fair value of the common stock vested	$ 5.4	$ 3.9	$ 2.6
Total intrinsic value of options exercised	12.8	1.1	$ 1.6
Total unrecognized compensation expense	$ 17.6	$ 9.8
Weighted-average period over which total unrecognized compensation expense is expected to be recognized	2 years 9 months 18 days	2 years 8 months 12 days
Stock Option \| Minimum
Assumptions used in estimating the fair value of each option award using the Black-Scholes option-pricing model
Fair value of common stock (in dollars per share)	$ 25.30	$ 12.98	$ 9.13
Stock Option \| Maximum
Assumptions used in estimating the fair value of each option award using the Black-Scholes option-pricing model
Fair value of common stock (in dollars per share)	$ 41.00	$ 22.80	$ 21.21

Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator, in thousands:
Net earnings used for calculation of basic EPS									$ 57,284	$ 91,221	$ 13,944
Interest expense on convertible debt									134	543	1,229
Changes in fair value of derivative liabilities									(76)	(448)	(589)
Loss on extinguishment of debt									295	671	2,338
Loss on extinguishment of outstanding debt, as if converted									(321)	(1,182)	(2,494)
Total adjustments									32	(416)	484
Net earnings used for calculation of diluted EPS									$ 57,316	$ 90,805	$ 14,428
Denominator:
Weighted average shares outstanding, basic									50,756,603	49,472,434	47,485,258
Effect of dilutive potential common shares:
Shares underlying Convertible Senior Secured Notes									285,257	1,222,363	2,459,009
Shares issuable to settle interest make-whole derivatives									7,012	71,537	804,507
Stock options and stock appreciation rights									2,252,278	942,649	411,606
Total potential dilutive common shares									2,544,547	2,236,549	3,675,122
Weighted average shares outstanding, diluted									53,301,150	51,708,983	51,160,380
Net earnings per share, basic	$ 0.27	$ 0.31	$ 0.34	$ 0.21	$ 0.29	$ 1.25	$ 0.21	$ 0.10	$ 1.13	$ 1.84	$ 0.29
Net earnings per share, diluted	$ 0.26	$ 0.29	$ 0.32	$ 0.19	$ 0.26	$ 1.18	$ 0.18	$ 0.08	$ 1.08	$ 1.76	$ 0.28
Warrants to purchase common stock
Income per share
Common stock equivalents excluded in the calculation of diluted income per share											20,957
Stock options, stock appreciation rights, and ESPP awards
Income per share
Common stock equivalents excluded in the calculation of diluted income per share									40,009	22,944	25,027

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of the income tax expense/(benefit)
U.S. corporate income tax rate (as a percent)		35.00%
Reduction in net deferred tax assets		$ 9,700
Current
Federal		18,288	$ 544	$ 624
State		3,822	78	42
Deferred
Federal		21,493	(39,898)
State		(269)	(1,576)
Income tax (benefit)/expense		43,334	(40,852)	666
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
Income tax expense computed at U.S. Federal statutory tax rate		35,217	17,629	5,114
Permanent items		(2,311)	715	601
State income taxes		2,714	(1,523)	42
Change in valuation allowance			(56,019)	(4,705)
Uncertain income tax position		(1,137)	143	533
Research and development credits		(2,196)	(1,902)	(979)
Other		1,353	105	60
Deferred rate change		9,694
Income tax expense/(benefit)		43,334	(40,852)	666
Research and development credit carryforwards		4,200
Available NOL's		51,000
Research and development credit carryforward available in 2019 to 2020		4,200
Federal income taxes paid			0	0
Accrued penalties related to uncertain tax positions		100
Deferred tax assets:
Net operating loss carryforward		5,072	24,926
Deferred rent credit		211	417
Accrued compensation and non-qualified stock options		7,090	8,128
Deferred financing costs			128
Depreciation and amortization		2,073	706
Research and development credits		3,795	7,119
Capitalized overhead into inventory (UNICAP 263A)		480	1,086
Nonrecourse liability related to sale of future royalties		6,377	11,223
Other		645	878
AMT credit		1,613	1,581
Accrued sales deductions		8,449
Net deferred tax asset		35,805	56,192
Deferred tax liability:
Debt discount on convertible notes			(141)
Infringement legal cost		(10,557)	(13,899)
Depreciation		(264)	(423)
Section 481(a)		(4,141)
Net deferred taxes		20,843	41,729
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at the beginning of the period	$ 8,859	9,299	9,341	8,964
Gross increases related to prior-year tax positions		947
Gross decreases related to prior-year tax positions			(375)	(5)
Gross increases related to current-year tax positions		1,178	662	646
Gross decreases related to current-year tax positions			(169)	(243)
Change in tax rates		(2,565)	(160)	(21)
Balance at the end of the period		8,859	9,299	$ 9,341
Alternate minimum tax expense on uncertain tax position		0	500
U.S. Federal
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
NOL carryforwards			32,100
NOL carryforwards after tax effect			6,700
Available from 2018 to 2020		32,100
State
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
NOL carryforwards			8,100
NOL carryforwards after tax effect			$ 500
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Tax expense on uncertain tax position		400
Minimum \| U.S. Federal
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
Available NOL's utilized per year in future years		7,100
Maximum \| U.S. Federal
Reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company's effective income tax rate
Available NOL's utilized per year in future years		$ 18,400
Forecast
Components of the income tax expense/(benefit)
U.S. corporate income tax rate (as a percent)	21.00%

Organization and Nature of Operations	12 Months Ended
Organization and Nature of Operations	Dec. 31, 2017
Organization and Nature of Operations
Organization and Nature of Operations	1. Organization and Nature of Operations Supernus Pharmaceuticals, Inc. (the Company) was incorporated in Delaware and commenced operations in 2005. The Company is a specialty pharmaceutical company focused on developing and commercializing products for the treatment of central nervous system (CNS) diseases. The Company markets two products, Oxtellar XR for the treatment of epilepsy and Trokendi XR for the prophylaxis of migraine headache and treatment of epilepsy, and has several proprietary product candidates in clinical development that address the psychiatry market. The Company launched Oxtellar XR and Trokendi XR in 2013 for the treatment of epilepsy and launched Trokendi XR for the prophylaxis of migraine headache in adolescents and adults in April 2017.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2017
Stockholders' Equity
Stockholders' Equity	9. Stockholders' Equity Common Stock The holders of our Common Stock are entitled to one vote for each share of Common Stock held. During the period from November 1, 2013 through December 31, 2017, the Company issued 17.0 million shares of Common Stock as a result of the conversion of approximately $90.0 million aggregate principal amount of Notes. In addition, the Company issued approximately 2.2 million shares of Common Stock in settlement of the interest-make whole provision associated with those conversions.

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2017
Employee Benefit Plan
Employee Benefit Plan	14. Employee Benefit Plan On January 2, 2006, the Company established the Supernus Pharmaceuticals, Inc. 401(k) Profit Sharing Plan (the 401(k) Plan) for its employees under Section 401(k) of the Internal Revenue Code (Code). Under the 401(k) Plan, all full-time employees who are at least 18 years old are eligible to participate in the 401(k) Plan. Employees may participate starting on the first day of the month following employment. Employees may contribute up to the lesser of 90% of eligible compensation or the applicable limit as established by the Code. Employees are 100% vested in their contributions to the 401(k) Plan. The Company matches 100% of a participant's contribution for the first 3% of their salary deferral and matches 50% of the next 2% of their salary deferral. As determined by the Board, the Company may elect to make a discretionary contribution not exceeding 60% of the annual compensation paid to all participating employees. The Company's contributions to the 401(k) Plan were approximately $1.8 million, $1.6 million, and $1.4 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Collaboration Agreements	12 Months Ended
Collaboration Agreements	Dec. 31, 2017
Collaboration Agreements
Collaboration Agreements	15. Collaboration Agreements In the third quarter of 2014, the Company received a $30.0 million payment pursuant to a Royalty Interest Acquisition Agreement related to the purchase by HC Royalty of certain of the Company's rights under the agreement with United Therapeutics Corporation related to the commercialization of Orenitram (treprostinil) Extended-Release Tablets. Full ownership of the royalty rights will revert to the Company if and when a certain threshold is reached per the terms of the Agreement. We have recorded a non-recourse liability related to this transaction of $30 million and have begun to amortize this amount to recognize non-cash royalty revenue as royalties are received by HC Royalty from United Therapeutics. We also recognized non-cash interest expense related to this liability that accrues at an effective interest rate, with that interest rate determined based on projections of HC Royalty's rate of return. We recognized non-cash royalty revenue of $5.3 million, $4.7 million and $3.0 million for the year ended December 31, 2017, 2016 and 2015, respectively. We recognized non-cash interest expense of $1.4 million $4.5 million and $3.5 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Organization and Nature of Operations (Details)	12 Months Ended
Organization and Nature of Operations (Details)	Dec. 31, 2017 product
Organization and Nature of Operations
Number of proprietary products in clinical development	2

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	51,314,850	49,971,267
Common stock, shares outstanding	51,314,850	49,971,267

Summary of Significant Accounting Policies - Segments (Details)	12 Months Ended
	Dec. 31, 2017 segment
Basis of Presentation
Number of operating segments	1

Summary of Significant Accounting Policies - SERP (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
SERP \| Other Non-current Assets
Marketable Securities - Restricted
Marketable securities	$ 335,000	$ 275,000

Summary of Significant Accounting Policies - Accounts Receivable, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, Net
Allowance for uncollectible receivables	$ 0	$ 42,000
Accounts receivable written off	0	0
Allowance for expected sales discounts	$ 8,900,000	$ 5,600,000
Revenues \| Customer Concentration Risk
Concentration risk percentage
Concentration risk percentage	97.00%
Revenues \| Customer Concentration Risk \| Customer A
Concentration risk percentage
Concentration risk percentage	30.00%
Revenues \| Customer Concentration Risk \| Customer B
Concentration risk percentage
Concentration risk percentage	30.00%
Revenues \| Customer Concentration Risk \| Customer C
Concentration risk percentage
Concentration risk percentage	37.00%
Accounts Receivable \| Customer Concentration Risk
Concentration risk percentage
Concentration risk percentage	96.00%
Accounts Receivable \| Customer Concentration Risk \| Customer A
Concentration risk percentage
Concentration risk percentage	46.00%
Accounts Receivable \| Customer Concentration Risk \| Customer B
Concentration risk percentage
Concentration risk percentage	22.00%
Accounts Receivable \| Customer Concentration Risk \| Customer C
Concentration risk percentage
Concentration risk percentage	28.00%

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Computer equipment
Property and equipment
Useful life	3 years
Software
Property and equipment
Useful life	3 years
Lab equipment and furniture \| Minimum
Property and equipment
Useful life	5 years
Lab equipment and furniture \| Maximum
Property and equipment
Useful life	10 years

Summary of Significant Accounting Policies - Deferred Financing Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	May 03, 2013
Deferred Financing Costs
Remaining outstanding balance		$ 4,165
7.50% Convertible Senior Secured Notes due 2019
Deferred Financing Costs
Interest rate (as a percent)	7.50%		7.50%
Remaining outstanding balance	$ 0	$ 4,165

Summary of Significant Accounting Policies - Recently Issued Accounting Pronouncements (Details) - USD ($)	Dec. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Recently Issued Accounting Pronouncements
Additional Paid in Capital	$ 294,999,000		$ 276,127,000
Retained Earnings (Accumulated Deficit)	(26,823,000)		(84,288,000)
Deferred Tax Assets, Net, Noncurrent	$ 20,843,000		$ 41,729,000
ASU 2016-09 \| Cumulative Effect Adjustment
Recently Issued Accounting Pronouncements
Additional Paid in Capital		$ 211,000
Retained Earnings (Accumulated Deficit)		211,000
ASU 2016-09 \| Deferred Tax Asset Adjustment
Recently Issued Accounting Pronouncements
Retained Earnings (Accumulated Deficit)		392,000
Deferred Tax Assets, Net, Noncurrent		$ 392,000

Fair Value of Financial Instruments - Carrying Value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Marketable securities	$ 39,736	$ 23,723
Liabilities:
Derivative liabilities		114
Total Carrying Value \| Recurring
Assets:
Cash and cash equivalents	100,304	66,398
Marketable securities	39,736	23,723
Corporate debt securities	132,477	74,343
Government debt securities	1,161	1,067
Marketable securities - restricted (SERP)	335	275
Total assets at fair value	274,013	165,806
Liabilities:
Derivative liabilities		114
Quoted Prices in Active Markets (Level 1) \| Recurring
Assets:
Cash and cash equivalents	100,304	66,398
Marketable securities	2,118	656
Corporate debt securities	448	1,717
Total assets at fair value	102,870	68,771
Significant Other Observable Inputs (Level 2) \| Recurring
Assets:
Marketable securities	37,618	23,067
Corporate debt securities	132,029	72,626
Government debt securities	1,161	1,067
Marketable securities - restricted (SERP)	335	275
Total assets at fair value	$ 171,143	97,035
Significant Unobservable Inputs (Level 3) \| Recurring
Liabilities:
Derivative liabilities		$ 114

Fair Value of Financial Instruments - Unrestricted Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value of Financial Instruments
Corporate and government debt securities, Amortized Cost	$ 174,235	$ 99,487
Corporate and government debt securities, Gross Unrealized Gains	48	86
Corporate and government debt securities, Gross Unrealized Losses	(909)	(440)
Corporate and government debt securities, Fair Value	173,374	99,133
Contractual maturities of the unrestricted available for sale marketable securities held
Less Than 1 Year	39,736
1 year to 2 years	42,921
2 year to 3 years	43,021
3 years to 4 years	47,696
Corporate debt securities, Fair Value	$ 173,374	$ 99,133

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventories
Raw materials	$ 2,995	$ 2,091
Work in process	8,873	8,874
Finished goods	4,436	5,836
Total inventories	$ 16,304	$ 16,801

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Property and equipment, gross	$ 14,470	$ 12,441
Less accumulated depreciation and amortization	(9,346)	(8,097)
Property and equipment, net	5,124	4,344
Depreciation and amortization expense	1,200	1,100	$ 700
Computer equipment
Property and equipment
Property and equipment, gross	1,226	1,206
Software
Property and equipment
Property and equipment, gross	2,004	1,807
Lab equipment and furniture
Property and equipment
Property and equipment, gross	8,331	6,758
Leasehold improvements
Property and equipment
Property and equipment, gross	2,731	2,642
Construction in progress
Property and equipment
Property and equipment, gross	$ 178	$ 28

Intangible Assets (Details) $ in Thousands	12 Months Ended
Intangible Assets (Details) $ in Thousands	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2017 item
Intangible Assets
Less accumulated Amortization	$ (8,166)	$ (1,283)
Net book value of intangible assets	36,019	36,350
Additional disclosures
Amortization expense	6,900	1,300	$ 200
Anticipated annual amortization expense for the next five years
2018	5,200
2019	5,200
2020	5,200
2021	5,200
2022	5,200
Trokendi XR patent litigation
Additional disclosures
Number of settlements \| item				2
Capitalized patent defense costs
Intangible Assets
Gross Carrying Amount	$ 44,185	$ 37,633
Minimum \| Capitalized patent defense costs
Intangible Assets
Weighted-Average Life	5 years 10 months 24 days	5 years 10 months 24 days
Maximum \| Capitalized patent defense costs
Intangible Assets
Weighted-Average Life	10 years	10 years

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses
Accrued compensation	$ 10,279	$ 9,145
Accrued professional fees	2,890	6,447
Accrued clinical trial and clinical supply costs	6,996	4,350
Accrued product costs	726	1,794
Accrued interest expense		61
Other accrued expenses	6,414	5,630
Total	$ 27,305	$ 27,427

Stockholders' Equity (Details) $ in Thousands	12 Months Ended		44 Months Ended	50 Months Ended
Stockholders' Equity (Details) $ in Thousands	Dec. 31, 2017 USD ($) item shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) item shares
7.50% Convertible Senior Secured Notes due 2019
Stockholders' equity
Shares of common stock issued in conversion of Notes	900,000	700,000		17,000,000
Principal amount of the Notes converted \| $	$ 4,575	$ 3,900	$ 85,425	$ 90,000
Shares of common stock issued in settlement of the interest make-whole provision		24,000		2,200,000
Common Stock
Stockholders' equity
Number of votes to which holders of common shares are entitled for each share held \| item	1			1

Share-Based Payments - 2012 Plan (Details) - 2012 Plan	12 Months Ended
Share-Based Payments - 2012 Plan (Details) - 2012 Plan	Dec. 31, 2017 installment shares
Share-based payments
Maximum number of shares of common stock provided for issuance \| shares	8,000,000
Stock Option
Share-based payments
Number of annual installments in which the awards would generally vest starting on the first anniversary of the date of grant \| installment	4
Stock Option \| Employees, Consultants and Advisors
Share-based payments
Contractual term	10 years
Stock Option \| Directors
Share-based payments
Contractual term	10 years
Vesting period	1 year

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Additional period for which the entity may elect to extend the term of the lease	5 years
Additional tenant improvement allowance	$ 2,100,000
Tenant improvement allowance utilized and included in fixed assets and deferred rent	79,000	$ 0	$ 200,000
Amount available for tenant improvements	400,000
Rent expense	2,700,000	$ 2,700,000	$ 2,600,000
Future minimum lease payments under non-cancelable operating leases
2018	3,349,000
2019	5,249,000
Thereafter	454,000
Total	9,052,000
Rune HealthCare Limited
Future minimum lease payments under non-cancelable operating leases
Milestone payments due	0
Afecta Pharmaceuticals Inc \| Maximum
Future minimum lease payments under non-cancelable operating leases
Potential maximum milestone payments payable	$ 300,000

Employee Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefit Plan (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit Plan
Minimum age requirement for employees to participate in the plan	18 years
Maximum contribution by employee (as a percent)	90.00%
Vesting percentage of contributions by employee to the 401(k) Plan	100.00%
Employer match of employee contributions on the first level of salary deferral (as a percent)	100.00%
Percentage of eligible compensation, first level, matched by employer	3.00%
Employer match of employee contributions on the second level of salary deferral (as a percent)	50.00%
Percentage of eligible compensation, second level, partially matched by employer	2.00%
Maximum percentage of participating employee annual compensation that the company may elect to make a discretionary contribute towards	60.00%
Company's contribution to the 401(k) Plan	$ 1.8	$ 1.6	$ 1.4

Collaboration Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Collaboration Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaboration agreement
Revenue From Royalty Agreement		$ 5,283	$ 4,686	$ 3,038
Noncash interest expense		$ 1,434	$ 4,548	$ 3,541
Collaborative Arrangement \| United Therapeutics
Collaboration agreement
Revenue From Royalty Agreement	$ 30,000
Non-recourse liability	$ 30,000