United Therapeutics (UTHR) 10-K 22 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 10, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	UNITED THERAPEUTICS Corp
Entity Central Index Key	1,082,554
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 4,094,026,937
Entity Common Stock, Shares Outstanding		44,961,616
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 1,023	$ 831.8
Marketable investments	27.8	122
Accounts receivable, no allowance for 2016 and 2015	214.5	192.8
Inventories, net	100	81.3
Other current assets	59.5	47.4
Total current assets	1,424.8	1,275.3
Marketable investments	2.3	38
Goodwill and other intangible assets, net	33.8	28.4
Property, plant, and equipment, net	489.3	495.8
Deferred tax assets, net	178.3	192.7
Other non-current assets	197.1	154.2
Total assets	2,325.6	2,184.4
Current liabilities:
Accounts payable and accrued expenses	104.2	103.4
Share tracking awards plan	194.8	274.5
Other current liabilities	33.5	62.8
Total current liabilities	332.5	440.7
Non-current liabilities:
Other non-current liabilities	130.9	144
Total liabilities	463.4	584.7
Commitments and contingencies-Note 9
Temporary equity	10.9	11.1
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 69,340,985 and 68,987,919 shares issued, and 42,965,856 and 45,760,845 shares outstanding at December 31, 2016 and 2015, respectively	0.7	0.7
Additional paid-in capital	1,813.5	1,790.6
Accumulated other comprehensive loss	(16.8)	(20.4)
Treasury stock, 26,375,129 and 23,227,074 shares at December 31, 2016 and 2015, respectively	(2,379.6)	(1,902.1)
Retained earnings	2,433.5	1,719.8
Total stockholders' equity	1,851.3	1,588.6
Total liabilities and stockholders' equity	2,325.6	2,184.4
Preferred stock
Stockholders' equity:
Preferred stock, par value $.01, 10,000,000 shares authorized, no shares issued
Series A junior participating preferred stock
Stockholders' equity:
Preferred stock, par value $.01, 10,000,000 shares authorized, no shares issued

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance (in dollars)	$ 0	$ 0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	245,000,000	245,000,000
Common stock, shares issued	69,340,985	68,987,919
Common stock, shares outstanding	42,965,856	45,760,845
Treasury stock, shares	26,375,129	23,227,074
Preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Series A junior participating preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000	100,000
Preferred stock, shares issued	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Net product sales	$ 1,598.8	$ 1,460.6	$ 1,279.5
Other		5.2	9
Total revenues	1,598.8	1,465.8	1,288.5
Operating expenses:
Cost of product sales	72.7	69	125.9
Research and development	147.6	245.1	242.5
Selling, general and administrative	316.8	452.7	381.3
Total operating expenses	537.1	766.8	749.7
Operating income	1,061.7	699	538.8
Other (expense) income:
Interest expense	(3.9)	(4.7)	(17.6)
Gain on sale of intangible asset		350
Other, net	2.4	0.1	4
Total other (expense) income, net	(1.5)	345.4	(13.6)
Income before income taxes	1,060.2	1,044.4	525.2
Income tax expense	(346.5)	(392.8)	(185.1)
Net income	$ 713.7	$ 651.6	$ 340.1
Net income per common share:
Basic (in dollars per share)	$ 16.29	$ 14.17	$ 7.06
Diluted (in dollars per share)	$ 15.25	$ 12.72	$ 6.28
Weighted average number of common shares outstanding:
Basic (in shares)	43.8	46	48.2
Diluted (in shares)	46.8	51.2	54.2

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Comprehensive income:
Net income	$ 713.7	$ 651.6	$ 340.1
Other comprehensive income (loss):
Foreign currency translation losses	(3)	(5.3)	(4.8)
Defined benefit pension plan:
Prior service cost arising during period, net of tax			(2.4)
Actuarial gain arising during period, net of tax	6	0.7	3
Amortization of actuarial gain and prior service cost included in net periodic pension cost, net of tax	0.6	0.9	0.9
Total defined benefit pension plan, net of tax	6.6	1.6	1.5
Unrealized loss on available-for-sale securities, net of tax			(0.3)
Other comprehensive income (loss), net of tax	3.6	(3.7)	(3.6)
Comprehensive income	$ 717.3	$ 647.9	$ 336.5

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings	Total
Balance at Dec. 31, 2013	$ 0.6	$ 1,057.2	$ (13.1)	$ (513.4)	$ 728.1	$ 1,259.4
Balance (in shares) at Dec. 31, 2013	63
Increase (Decrease) in Stockholders' Equity
Net income					340.1	340.1
Foreign currency translation adjustments			(4.8)			(4.8)
Unrealized gain on available-for-sale securities			(0.3)			(0.3)
Defined benefit pension plan			1.5			1.5
Shares issued under employee stock purchase plan		3.3				3.3
Conversion of 2016 convertible notes	$ 0.1	192.9		(189.3)		3.7
Conversion of 2016 convertible notes (in shares)	1.5
Equity component - 2016 convertible notes		11.1				11.1
Repurchase of shares				(483.1)		(483.1)
Exercise of stock options		50.2				50.2
Exercise of stock options (in shares)	1.5
Tax benefit from exercises of non-qualified stock options		30.8				30.8
Share-based compensation		30.6				30.6
Balance at Dec. 31, 2014	$ 0.7	1,376.1	(16.7)	(1,185.8)	1,068.2	1,242.5
Balance (in shares) at Dec. 31, 2014	66
Increase (Decrease) in Stockholders' Equity
Net income					651.6	651.6
Foreign currency translation adjustments			(5.3)			(5.3)
Defined benefit pension plan			1.6			1.6
Shares issued under employee stock purchase plan		4				4
Conversion of 2016 convertible notes		324.7		(321.8)		2.9
Conversion of 2016 convertible notes (in shares)	2
Equity component - 2016 convertible notes		3				3
Repurchase of shares				(394.5)		(394.5)
Exercise of stock options		39.3				39.3
Exercise of stock options (in shares)	1
Tax benefit from exercises of non-qualified stock options		37.4				37.4
Share-based compensation		6.1				6.1
Balance at Dec. 31, 2015	$ 0.7	1,790.6	(20.4)	(1,902.1)	1,719.8	1,588.6
Balance (in shares) at Dec. 31, 2015	69
Increase (Decrease) in Stockholders' Equity
Net income					713.7	713.7
Foreign currency translation adjustments			(3)			(3)
Defined benefit pension plan			6.6			6.6
Shares issued under employee stock purchase plan		4.3				4.3
Conversion of 2016 convertible notes		7.6		(7.5)		0.1
Conversion of 2016 convertible notes (in shares)	0.1
Equity component - 2016 convertible notes		0.1				0.1
Shares issued upon expiration of warrants		(30)		30
Repurchase of shares				(500)		(500)
Exercise of stock options		7.7				7.7
Exercise of stock options (in shares)	0.2
Tax benefit from exercises of non-qualified stock options		5.9				5.9
Share-based compensation		27.3				27.3
Balance at Dec. 31, 2016	$ 0.7	$ 1,813.5	$ (16.8)	$ (2,379.6)	$ 2,433.5	$ 1,851.3
Balance (in shares) at Dec. 31, 2016	69.3

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 713.7	$ 651.6	$ 340.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31.6	32.9	32.2
Share-based compensation expense	12.1	280.3	190.1
Gain on sale of intangible asset		(350)
Other	9.5	7.5	24.2
Excess tax benefits from share-based compensation	(5.9)	(37.4)	(30.8)
Changes in operating assets and liabilities:
Accounts receivable	(21.7)	(30.5)	(35.7)
Inventories	(24.5)	(6.8)	(21)
Accounts payable and accrued expenses	0.6	17	(6.8)
Other assets and liabilities	(71.8)	(181.8)	(137)
Net cash provided by operating activities	643.6	382.8	355.3
Cash flows from investing activities:
Purchases of property, plant and equipment	(38)	(49.8)	(47.4)
Purchases of held-to-maturity investments	(0.8)	(62.8)	(118.7)
Maturities of held-to-maturity investments	130.4	320.4	549.6
Gain on sale of intangible asset		350
Purchase of investments held at cost	(36)	(54.2)	(45)
Purchase of investments under the equity method	(2.1)
Intangible assets acquired, net	(5.2)
Net cash provided by investing activities	48.3	503.6	338.5
Cash flows from financing activities:
Principal payments of debt	(8.8)	(133.2)	(177.8)
Payments of debt issuance costs	(6.8)
Payments to repurchase common stock	(500)	(394.5)	(483.1)
Proceeds from line of credit			140
Payments on line of credit			(140)
Proceeds from exercise of stock options	7.7	39.3	50.2
Issuance of stock under employee stock purchase plan	4.3	4	3.3
Excess tax benefits from share-based compensation	5.9	37.4	30.8
Net cash used in financing activities	(497.7)	(447)	(576.6)
Effect of exchange rate changes on cash and cash equivalents	(3)	(5.3)	(3.8)
Net increase in cash and cash equivalents	191.2	434.1	113.4
Cash and cash equivalents, beginning of year	831.8	397.7	284.3
Cash and cash equivalents, end of year	1,023	831.8	397.7
Supplemental cash flow information:
Cash paid for interest	1.5	1	5.5
Cash paid for income taxes	362.4	293.3	195.6
Non-cash investing and financing activities:
Acquisitions-non-cash consideration			5.2
Non-cash additions to property, plant and equipment	2.9	1.1	3.2
Issuance of common stock upon conversion of convertible notes	$ 7.5	$ 321.8	$ 189.3

Organization and Business Descr

Organization and Business Description	12 Months Ended
	Dec. 31, 2016
Organization and Business Description
Organization and Business Description	1. Organization and Business Description United Therapeutics Corporation is a biotechnology company focused on the development and commercialization of innovative products to address the unmet medical needs of patients with chronic and life-threatening conditions. We have approval from the U.S. Food and Drug Administration (FDA) to market the following therapies: Remodulin ® (treprostinil) Injection (Remodulin), Tyvaso ® (treprostinil) Inhalation Solution (Tyvaso), Adcirca ® (tadalafil) Tablets (Adcirca), Orenitram ® (treprostinil) Extended-Release Tablets (Orenitram) and Unituxin ® (dinutuximab) Injection (Unituxin). Our only significant revenues outside the United States are derived from sales of Remodulin in Europe. We commenced commercial sales of Orenitram and Unituxin during the second quarter of 2014 and third quarter of 2015, respectively. As used in these notes to the consolidated financial statements, unless the context otherwise requires, the terms "we", "us", "our", and similar terms refer to United Therapeutics Corporation and its consolidated subsidiaries.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements of United Therapeutics Corporation and its wholly owned subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States (GAAP). All intercompany balances and transactions have been eliminated in consolidation. In the current liabilities section of our balance sheet, we reclassified the prior period amount within "convertible notes" to "other current liabilities" to conform with the current period presentation. Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We base our estimates on assumptions regarding historical experience, currently available information and anticipated developments that we believe are reasonable and appropriate. However, because the use of estimates involves an inherent degree of uncertainty, actual results could differ from those estimates. Our significant accounting policies that require use of subjective and/or complex judgment and estimates impact the following financial statement areas: revenue recognition, share-based compensation, marketable investments, fair value measurements (including those relating to our acquisitions), income taxes, goodwill and other intangible assets, and obligations related to our Supplemental Executive Retirement Plan. Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses approximate fair value because of their short maturities. The fair values of our marketable investments, 1.0 percent Convertible Senior Notes which matured in September 2016 (Convertible Notes) and contingent consideration are reported in Note 4—Investments and Note 5—Fair Value Measurements, respectively. Fair Value Measurements Fair value is a market-based measurement, not an entity-specific measurement. The objective of a fair value measurement is to estimate the price to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date under current market conditions. Such transactions to sell an asset or transfer a liability are assumed to occur in the principal market for that asset or liability, or in the absence of the principal market, the most advantageous market for the asset or liability. Assets and liabilities subject to fair value measurement disclosures are required to be classified according to a three-level fair value hierarchy with respect to the inputs (or assumptions) used to determine fair value. The level in which an asset or liability is disclosed within the fair value hierarchy is based on the lowest level input that is significant to the related fair value measurement in its entirety. The guidance under the fair value measurement framework applies to other existing accounting guidance in the Financial Accounting Standards Board (FASB) codification that requires or permits fair value measurements. Refer to related disclosures in Note 5—Fair Value Measurements to these consolidated financial statements. Cash Equivalents Cash equivalents consist of highly liquid investments with maturities of three months or less from the date of acquisition and include money market funds, commercial paper, and certificates of deposit. Marketable Investments Substantially all of our marketable investments are debt securities that we classify as held-to-maturity because of our positive intent and ability to hold the securities until maturity. Held-to-maturity securities are classified as either current or non-current assets on our consolidated balance sheets based on their contractual maturity dates and are recorded at amortized cost, adjusted for the amortization of discounts or premiums. Related discounts and premiums are amortized over the term of these securities as an adjustment to the yield using the effective interest method. We monitor our investment portfolio for impairment quarterly or more frequently if circumstances warrant. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, we record an impairment charge within earnings attributable to the estimated credit loss. In determining whether a decline in the value of an investment is other-than-temporary, we evaluate currently available factors that may include, among others: (1) general market conditions; (2) the duration and extent to which fair value has been less than the carrying value; (3) the investment issuer's financial condition and business outlook; and (4) our assessment as to whether it is more likely than not that we will be required to sell a security prior to recovery of its amortized cost basis. Trade Receivables Trade receivables consist of short-term amounts due from customers and are stated at the amount we expect to collect. We establish an allowance for doubtful accounts, if any, based on our assessment of the collectability of specific customer accounts. Inventories Inventories are stated at the lower of cost (first-in, first-out method) or market (current replacement cost) and consist of the following, net of reserves (in millions): As of 2016 2015 Raw materials $ $ Work-in-progress Finished goods ​ ​ ​ ​ ​ ​ ​ ​ Total inventories $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Goodwill and Other Intangible Assets The carrying amount of goodwill is not amortized but is subject to annual impairment testing. We conduct our impairment testing of goodwill annually during the fourth quarter, or more frequently, if impairment indicators exist. Initially, we evaluate various pertinent qualitative factors to assess whether it is more likely than not that the fair value of a reporting unit to which goodwill has been assigned is less than its carrying value. Such qualitative factors can include, among others: (1) industry and market conditions; (2) present and anticipated sales and cost factors; and (3) overall financial performance. If we conclude based on our qualitative assessment that it is more likely than not that the fair value of a reporting unit is less than its carrying value, we then measure the fair value of the reporting unit and compare its fair value to its carrying value (Step 1 of the goodwill impairment test). If the carrying amount of the reporting unit exceeds its fair value, then the amount of an impairment loss, if any, is measured as the excess of the recorded amount of goodwill over its implied fair value (Step 2 of the goodwill impairment test). We used a qualitative assessment for our goodwill impairment testing for 2016 and 2015. Our evaluation of goodwill completed during the years ended December 31, 2016 and 2015, resulted in no impairment losses. Indefinite-lived intangible assets are not amortized but are evaluated annually or more frequently for impairment if impairment indicators exist. Our indefinite-lived intangible assets include purchased in-process research and development projects, which were measured at their estimated fair values as of their acquisition dates. We used a qualitative assessment for our indefinite-lived intangible asset impairment testing. Our evaluation of indefinite-lived intangible assets completed during the years ended December 31, 2016 and 2015, resulted in no impairment losses. Intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an intangible asset may not be recoverable. Impairment losses are measured and recognized to the extent the carrying value of such assets exceeds their fair value. We recorded no impairment losses during the years ended December 31, 2016 and 2015. Goodwill and other intangible assets consists of the following (in millions): As of December 31, 2016 As of December 31, 2015 Gross Accumulated Net Gross Accumulated Net Goodwill $ $ — $ $ $ — $ Other intangible assets: Technology, patents and trade names ) ) In-process research and development — — Customer relationships and non-compete agreements ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ) $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Related amortization expense for the years ended December 31, 2016, 2015 and 2014, was $0.6 million, $1.1 million and $1.4 million, respectively. As of December 31, 2016, aggregate amortization expense relating to definite-lived intangible assets for each of the five succeeding years and thereafter is estimated at less than $1.0 million per year. In September 2015, we sold for $350.0 million in cash the Rare Pediatric Priority Review Voucher (PPRV) we received from the FDA in connection with the approval of Unituxin. The proceeds from the sale of the PPRV were recognized as a gain on the sale of an intangible asset as the PPRV did not have a carrying value on our consolidated balance sheet at the time of sale. Property, Plant and Equipment Property, plant and equipment is recorded at cost and depreciated over its estimated useful life using the straight-line method. The estimated useful lives of property, plant and equipment by major category are as follows: Land improvements 15 Years Buildings 25 - 39 Years Building improvements 10 - 39 Years Furniture, equipment and vehicles 3 - 25 Years Leasehold improvements Remaining lease term, or the estimated useful life of the improvement, whichever is shorter Property, plant and equipment consists of the following (in millions): As of December 31, 2016 2015 Land and land improvements $ $ Buildings, building improvements and leasehold improvements Buildings under construction Furniture, equipment and vehicles ​ ​ ​ ​ ​ ​ ​ ​ Less—accumulated depreciation ) ) ​ ​ ​ ​ ​ ​ ​ ​ Property, plant and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation expense for the years ended December 31, 2016, 2015 and 2014, was $31.0 million, $31.8 million and $30.8 million, respectively. Buildings under construction consists of direct costs relating to our construction projects. Treasury Stock Repurchased treasury stock is recorded at cost, including commissions and fees. Treasury stock acquired in connection with the convertible note hedge on our Convertible Notes is recorded at the fair value on the acquisition date, which is the closing price of our common stock on that date. The cost of treasury shares sold or reissued is determined using the first-in, first-out method. Related gains and losses on sales of treasury stock are recognized as adjustments to stockholders' equity. Revenue Recognition Remodulin, Tyvaso, Orenitram and Unituxin We sell Remodulin, Tyvaso, Orenitram and Unituxin to distributors under similar contractual arrangements. We recognize sales of these products when title and risk of ownership pass to our distributors upon satisfactory delivery— i.e., when all of our performance obligations under our distribution agreements have been satisfied. We record sales of these products net of various product sales allowances in the period that associated revenues are recognized. These sales allowances include estimated rebates, prompt payment discounts and service fees paid to our distributors. Calculating these sales allowances involves the use of significant estimates and judgments and information obtained from external sources. We derive our provisions for estimated rebates from an analysis of historical levels of rebates to both state Medicaid agencies and commercial third-party payers by product, relative to sales of each product. In addition, for Orenitram patients, we determine our obligation for prescription drug discounts required by Medicare Part D for patients within the coverage gap based on estimations of the number of patients and the period that such patients will remain within the coverage gap. In formulating our estimates, we also consider the impact of anticipated changes in our product pricing, if any, sales trends and government rebate programs, particularly as they relate to eligibility requirements and/or rebate pricing. Prompt pay discounts are estimated based on our experience with sales to eligible distributors. Our distributors have routinely taken advantage of these discounts and we expect them to continue to do so. We pay our distributors for contractual services rendered and accrue for related fees based on contractual rates applied to the estimated units of service provided by distributors for a given financial reporting period. Our distributors do not possess return rights for Remodulin, Tyvaso and Orenitram; however, the sales terms for Unituxin include return rights that extend throughout the distribution channel. The financial impact of return rights for Unituxin is not material. We also provide exchange rights for all products in the event that a product is damaged during shipment or expires. Exchanges for damaged product are highly infrequent and the impact of expired product is not material. We do not record a reserve for estimated exchange rights for any of these products in the period of sale. Adcirca Adcirca is manufactured for us by Eli Lilly and Company (Lilly) and distributed through Lilly's pharmaceutical wholesaler network. Specifically, Lilly handles all of the administrative functions associated with the sale of Adcirca on our behalf, including the receipt and processing of customer purchase orders, shipment to customers, and invoicing and collection of customer payments. In addition, the sales terms for Adcirca include return rights that extend throughout the distribution channel. We recognize sales of Adcirca on a gross basis (net of allowances) upon delivery to customers due to the following factors: (1) we are responsible for the acceptability of the product purchased by wholesalers; (2) we bear all inventory risk, as title and risk of loss pass to us at the shipping point from Lilly's manufacturing facility; (3) we assume credit risk if Lilly is unable to collect amounts due from customers; and (4) we assume the risk and cost of a product recall, if required. We recognize sales of Adcirca net of: (1) estimated rebates under government drug discount programs and commercial third-party payer contracts; (2) prompt pay discounts; (3) allowances for product returns; and (4) wholesaler fees. We estimate our liability for rebates based on an analysis of historical levels of rebates to both Medicaid and commercial third-party payers and we consider the impact of sales trends, changes in government and commercial rebate programs and anticipated changes in Adcirca's pricing. Prompt pay discounts are estimated based on our experience with sales to eligible distributors. We derive our allowance for returns based on historical return rates accumulated since the commercial launch of Adcirca in 2009. Wholesaler fees are based on contractual percentages of sales to wholesalers. Research and Development Research and development costs are expensed as incurred except for refundable payments made in advance of services to be provided to us. Related expenses consist of internal labor and overhead, costs to acquire pharmaceutical products and product rights for development, materials used in clinical trials and amounts paid to third parties for services and materials relating to drug development and clinical trials. We recognize the following as research and development expense in the period related costs are incurred: • costs associated with in-house or contracted manufacturing activities prior to receiving FDA approval for such facilities, or for major unproven changes to our manufacturing processes; • costs incurred in licensing the rights to technologies in the research and development stage that have no alternative future use; and • up-front payments made in connection with arrangements to obtain license and distribution rights to pharmaceutical product candidates prior to regulatory approval, absent any alternative future use. Share-Based Compensation Our share tracking awards plans require cash settlement upon exercise and are classified as a liability. Accordingly, the fair value of related cash-settled awards is re-measured at each reporting date until awards are exercised or are otherwise no longer outstanding. Related changes in the fair value of outstanding cash-settled awards at each financial reporting date are recognized as adjustments to share-based compensation expense. Generally, the fair value of a stock option grant is measured on its grant date and related compensation expense is recognized ratably over the requisite service period. We issue new shares of our common stock upon the exercise of stock options. We measure the fair value of restricted stock units using the stock price on the date of grant and related compensation expense is recognized ratably over the vesting period. Each restricted stock unit entitles the holder to receive one share of our common stock upon vesting. We issue new shares of our common stock upon the vesting of restricted stock units. We measure the fair value of stock to be purchased through our employee stock purchase plan at the beginning of an offering period, or grant date, and recognize related compensation expense ratably over the requisite service period (the offering period). We issue new shares of our common stock upon the end of each offering period, or exercise date. Income Taxes Income taxes are accounted for in accordance with the asset and liability method. Accordingly, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance when, in our judgment, it is more likely than not that some or all of the deferred tax assets will not be realized. Financial statement recognition of a tax position taken or expected to be taken in a tax return is determined based on a more likely than not threshold of that position being sustained. If the tax position meets this threshold, the benefit to be recognized is measured as the largest amount that is more likely than not to be realized upon ultimate settlement. It is our policy to record interest and penalties related to uncertain tax positions as a component of income tax expense. Earnings (Loss) per Share Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period, plus the potential dilutive effect of other securities if such securities were converted or exercised. During periods in which we incur net losses, both basic and diluted loss per share is calculated by dividing the net loss by the weighted average shares outstanding—potentially dilutive securities are excluded from the calculation because their effect would be anti-dilutive. Concentration of Credit Risk Financial instruments that are exposed to credit risk consist of cash, money market funds, commercial paper, marketable investments, and trade receivables. We maintain our cash and money market funds with financial institutions that are federally insured. While balances deposited in these institutions often exceed Federal Deposit Insurance Corporation limits, we have not experienced any losses on related accounts to date. Furthermore, we limit our risk exposure by maintaining funds in financial institutions that we believe are creditworthy and financially sound. Our investments in marketable debt securities have been issued by corporate entities and federally-sponsored enterprises with high credit ratings. We mitigate investment risks by investing in highly-rated securities with relatively short maturities that we believe do not subject us to undue investment or credit risk. In addition, our investment policy does not provide for investments in complex or structured financial instruments. At any given time, our trade receivables are concentrated among a small number of principal customers. If any of these financial institutions, issuers or customers fail to perform their obligations under the terms of these financial instruments, our maximum exposure to potential losses would be equal to amounts reported on our consolidated balance sheets.

Recently Issued Accounting Stan

Recently Issued Accounting Standards	12 Months Ended
	Dec. 31, 2016
Recently Issued Accounting Standards
Recently Issued Accounting Standards	3. Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers and subsequent clarifying guidance. This guidance eliminates transaction-specific and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. This guidance requires that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. In addition, disclosure is required about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. This guidance is effective for annual reporting periods beginning after December 15, 2017, and allows for either full retrospective or modified retrospective adoption. We are evaluating the transition method we will elect and the effects of the adoption of this ASU on our financial statements. An assessment of our customer arrangements has been initiated and we are currently evaluating the impact on our financial statements. In July 2015, the FASB issued ASU No. 2015-11, Simplifying the Measurement of Inventory (ASU 2015-11), which requires that inventory be measured at the lower of cost or net realizable value for entities using first-in, first-out or average cost methods. ASU 2015-11 should be applied prospectively and will be effective for fiscal years beginning after December 15, 2016, and for interim periods within those fiscal years, with early adoption permitted. We adopted this standard on January 1, 2017. The provisions of this standard do not have a material impact on our financial statements. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments—Overall: Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01), which requires equity investments to be measured at fair value through net income. Equity investments that are accounted for under the equity method are not impacted. ASU 2016-01 provides that equity investments without readily determinable fair values can be valued at cost minus impairment with a simplified impairment assessment using qualitative assessments. ASU 2016-01 requires separate presentation of the financial assets and liabilities by category and form. ASU 2016-01 should be applied prospectively and will be effective for fiscal years beginning after December 15, 2017, and for interim periods within those fiscal years. Early adoption is not permitted except in limited circumstances. We are evaluating the effect of adoption on our financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02), which requires that organizations recognize lease assets and lease liabilities on the balance sheet. ASU 2016-02 also requires additional quantitative and qualitative disclosures that provide the amount, timing, and uncertainty of cash flows relating to lease arrangements. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018, using a modified retrospective approach. The modified retrospective approach requires retrospective application to the earliest period presented in the respective financial statements, provides certain practical expedients related to leases that commenced prior to the effective date and allows the use of hindsight when evaluating lease options. Early adoption is permitted. We are evaluating the effect of adoption on our financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (ASU 2016-09), which serves to simplify the accounting for share-based payment transactions. ASU 2016-09 includes guidance on several aspects of the accounting for share-based payments, including the income tax consequences, forfeitures and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, and for interim periods within those fiscal years. We adopted this standard on January 1, 2017. Upon adoption of ASU 2016-09, we will recognize excess tax benefits as income tax benefits and expenses on the consolidated statements of operations. Previously, such amounts were recognized as increases and decreases in additional paid-in capital on the consolidated balance sheets. On January 1, 2017, we also established an accounting policy election to account for forfeitures when they occur. As a result, we will recognize a cumulative-effect adjustment to reduce retained earnings for the effect of the forfeiture estimate on awards that were in the process of vesting as of December 31, 2016. Although it is difficult to predict the impact of adopting ASU 2016-09 because the impact depends on the timing of when employees exercise stock options, when employees forfeit stock options and the fair value of our stock price at such time, we do not anticipate a material impact on our financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows—Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15), which reduces existing diversity in the classification of certain cash receipts and cash payments on the statements of cash flows. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and for interim periods within those fiscal years. Early adoption is permitted. We are evaluating the effect of adoption on our financial statements. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes—Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16), which requires that an entity recognize the income tax consequences of an intra-entity transfer of assets other than inventory when the transfer occurs. ASU 2016-16 is effective for annual reporting periods beginning after December 15, 2017 using a modified retrospective approach through a cumulative adjustment in retained earnings as of the beginning of the period of adoption. Early adoption is permitted. We are evaluating the effect of adoption on our financial statements.

Investments

Investments	12 Months Ended
	Dec. 31, 2016
Investments
Investments	4. Investments Marketable Investments Held-to-Maturity Investments Marketable investments classified as held-to-maturity consist of the following (in millions): As of December 31, 2016 Amortized Gross Gross Fair Government-sponsored enterprises $ $ — $ — $ Corporate notes and bonds — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported under the following captions on the consolidated balance sheet: Current marketable investments $ Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2015 Amortized Gross Gross Fair Government-sponsored enterprises $ $ — $ ) $ Corporate notes and bonds — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported under the following captions on the consolidated balance sheet: Current marketable investments $ Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following table summarizes gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position (in millions): As of December 31, 2016 2015 Fair Gross Fair Gross Government-sponsored enterprises: Continuous unrealized loss position less than one year $ — $ — $ $ ) Continuous unrealized loss position greater than one year — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — — ) Corporate notes and bonds: Continuous unrealized loss position less than one year — — — Continuous unrealized loss position greater than one year — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ — $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ We attributed the unrealized losses on held-to-maturity securities as of December 31, 2015, to the variability in related market interest rates. We did not intend to sell these securities, nor was it more likely than not that we were required to sell them prior to the end of their contractual terms. Furthermore, we did not believe that these securities exposed us to undue market risk or counterparty credit risk. As such, we did not consider these securities to be other than temporarily impaired. The following table summarizes the contractual maturities of held-to-maturity marketable investments (in millions): As of Amortized Fair Due in less than one year $ $ Due in one to two years Due in three to five years — — Due after five years — — ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investments Held at Cost As of December 31, 2016, we maintain in the aggregate, non-controlling equity investments of approximately $173.2 million in privately-held companies, including a $100.0 million investment in the preferred stock of Synthetic Genomics, Inc. (SGI), which we purchased in two separate $50.0 million transactions in May 2014 and September 2015. These investments are held at cost since we do not have the ability to exercise significant influence over these companies and their fair values are not readily determinable. The fair value of these investments has not been estimated at December 31, 2016, as we have not identified any events or developments indicating that their carrying amounts may be impaired. We include these investments within other non-current assets on our accompanying consolidated balance sheets. In addition to the SGI investments noted above, we entered into a separate multi-year research and development collaboration agreement with SGI in May 2014, whereby SGI will develop engineered primary pig cells with modified genomes for use in our xenotransplantation program. This collaboration was initially focused primarily on lungs and was expanded in September 2015 to include an additional focus on kidneys. Under this agreement, each party assumes its own research and development costs and SGI may receive royalties and milestone payments from development and commercialization of organs. During the year ended December 31, 2016, we made payments of $36.0 million for investments held at cost.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Fair Value Measurements	5. Fair Value Measurements Assets and liabilities subject to fair value measurements are required to be disclosed within a fair value hierarchy. The fair value hierarchy ranks the quality and reliability of inputs used to determine fair value. Accordingly, assets and liabilities carried at, or permitted to be carried at, fair value are classified within the fair value hierarchy in one of the following categories based on the lowest level input that is significant in measuring fair value: Level 1—Fair value is determined by using unadjusted quoted prices that are available in active markets for identical assets and liabilities. Level 2—Fair value is determined by using inputs other than Level 1 quoted prices that are directly or indirectly observable. Inputs can include quoted prices for similar assets and liabilities in active markets or quoted prices for identical assets and liabilities in inactive markets. Related inputs can also include those used in valuation or other pricing models such as interest rates and yield curves that can be corroborated by observable market data. Level 3—Fair value is determined by using inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgment. We account for certain assets and liabilities at fair value and rank these assets and liabilities within the fair value hierarchy. Other current assets and other current liabilities have fair values that approximate their carrying values. Assets and liabilities subject to fair value measurements are as follows (in millions): As of December 31, 2016 Level 1 Level 2 Level 3 Balance Assets Money market funds (1) $ $ — $ — $ Federally-sponsored and corporate debt securities (2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities Contingent consideration (4) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2015 Level 1 Level 2 Level 3 Balance Assets Money market funds (1) $ $ — $ — $ Federally-sponsored and corporate debt securities (2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities Convertible notes due 2016 (3) $ $ — $ — $ Contingent consideration (4) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Included in cash and cash equivalents on the accompanying consolidated balance sheets. (2) Included in current and non-current marketable investments on the accompanying consolidated balance sheets. The fair value of these securities is principally measured or corroborated by trade data for identical securities in which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded. See also Note 4—Investments—Marketable Investments—Held-to-Maturity Investments to these consolidated financial statements. (3) Included in other current liabilities on the accompanying consolidated balance sheets. The Convertible Notes matured on September 15, 2016. The carrying value of the Convertible Notes as of December 31, 2015 was $5.4 million. The fair value of our Convertible Notes was estimated using Level 1 observable inputs since our Convertible Notes were trading with sufficient frequency such that we believed related pricing could be used as the primary basis for measuring their fair value. As of December 31, 2015, the fair value of the Convertible Notes was substantially higher than their book value. This was primarily due to the excess conversion value of the Convertible Notes compared to the Convertible Notes' par value, and the fact that any such excess would be paid in shares of our common stock. (4) Included in other non-current liabilities on the accompanying consolidated balance sheets. The fair value of contingent consideration has been estimated using probability weighted discounted cash flow models (DCF). The DCF incorporates Level 3 inputs including estimated discount rates that we believe market participants would consider relevant in pricing and the projected timing and amount of cash flows, which are estimated and developed, in part, based on the requirements specific to each acquisition agreement. We analyze and evaluate these fair value measurements quarterly to determine whether valuation inputs continue to be relevant and appropriate or whether current period developments warrant adjustments to valuation inputs and related measurements.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2016
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Expenses	6. Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following by major categories (in millions): As of 2016 2015 Accounts payable $ $ Accrued expenses: Sales related (royalties, rebates and fees) $ $ Payroll related Other ​ ​ ​ ​ ​ ​ ​ ​ Total accrued expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ Total accounts payable and accrued expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Share Tracking Awards Plans

Share Tracking Awards Plans	12 Months Ended
	Dec. 31, 2016
Share Tracking Awards Plans
Share Tracking Awards Plans	7. Share Tracking Awards Plans We previously issued awards under the United Therapeutics Corporation Share Tracking Awards Plan, adopted in June 2008 (2008 STAP) and the United Therapeutics Corporation 2011 Share Tracking Awards Plan, adopted in March 2011 (2011 STAP). We refer to the 2008 STAP and the 2011 STAP collectively as the "STAP" and awards granted and/or outstanding under either of these plans as "STAP awards." STAP awards convey the right to receive in cash an amount equal to the appreciation of our common stock, which is measured as the increase in the closing price of our common stock between the dates of grant and exercise. STAP awards expire on the tenth anniversary of the grant date, and in most cases they vest in equal increments on each anniversary of the grant date over a four-year period. The STAP liability includes vested awards and awards that are expected to vest. We recognize expense for awards that are expected to vest during the vesting period. We discontinued the issuance of STAP awards in June 2015, when our shareholders approved the United Therapeutics Corporation 2015 Stock Incentive Plan (the 2015 Plan), a broad-based stock incentive plan enabling us to grant stock options and other forms of equity compensation to our employees. See Note 11—Stockholders' Equity to these consolidated financial statements for information on the 2015 Plan. The aggregate balance of the STAP liability was $268.9 million and $354.7 million at December 31, 2016 and 2015, respectively, of which $74.1 million and $80.2 million, respectively, has been classified as other non-current liabilities on our consolidated balance sheets based on their vesting terms. Estimating the fair value of STAP awards requires the use of certain inputs that can materially impact the determination of fair value and the amount of compensation expense (benefit) we recognize. Inputs used in estimating fair value include the price of our common stock, the expected volatility of the price of our common stock, the risk-free interest rate, the expected term of STAP awards, the expected forfeiture rate and the expected dividend yield. The fair value of the STAP awards is measured at the end of each financial reporting period because the awards are settled in cash. A description of the key inputs, requiring estimates, used in determining the fair value of the awards is provided below: Expected volatility —Volatility is a measure of the amount the price of our common stock has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. We use historical volatility based on weekly price observations of our common stock during the period immediately preceding an award that is equal to its expected term up to a maximum period of five years. We believe the volatility in the price of our common stock over the preceding five years generally provides a reliable projection of future long-term volatility. Risk-free interest rate —The risk-free interest rate is the average interest rate consistent with the yield available on a U.S. Treasury note with a term equal to the expected term of an award. Expected term —The expected term reflects the estimated time period we expect an award to remain outstanding. For the years ended December 31, 2016, 2015 and 2014, we used historical data to develop this input. Expected forfeiture rate —The expected forfeiture rate is an estimated percentage of awards granted that are expected to be forfeited or canceled on an annual basis prior to becoming fully vested. We derive our estimate based on historical forfeiture experience for similar classes of employees. Expected dividend yield —We do not pay cash dividends on our common stock and do not expect to do so in the future. Therefore, the dividend yield is zero. The table below includes the weighted-average assumptions used to measure the fair value of the outstanding STAP awards: As of December 31, 2016 2015 2014 Expected volatility % % % Risk-free interest rate % % % Expected term of awards (in years) Expected forfeiture rate % % % Expected dividend yield % % % The closing price of our common stock was $143.43, $156.61, and $129.49 on December 31, 2016, 2015, and 2014, respectively. A summary of the status and activity of the STAP is presented below: Number of Weighted- Weighted Aggregate Outstanding at January 1, 2016 $ Granted — — Exercised ) Forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The weighted average grant-date fair value of STAP awards granted during the years ended December 31, 2015 and 2014 was $58.52 and $33.82, respectively. Share-based compensation (benefit) expense recognized in connection with the STAP is as follows (in millions): Year Ended December 31, 2016 2015 2014 Cost of product sales $ — $ $ Research and development ) Selling, general and administrative ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation (benefit) expense before tax ) Related income tax expense (benefit) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation (benefit) expense, net of tax $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation capitalized as part of inventory $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid to settle STAP exercises during the years ended December 31, 2016, 2015 and 2014 was $69.5 million, $248.8 million, and $144.1 million, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt
Debt	8. Debt Unsecured Revolving Credit Facility In January 2016, we entered into a credit agreement (the 2016 Credit Agreement) with Wells Fargo Bank, National Association (Wells Fargo), as administrative agent and a swingline lender, and various other lender parties, providing for an unsecured revolving credit facility of up to $1.0 billion. In accordance with the terms of the 2016 Credit Agreement, we extended the maturity date by one year effective in January 2017. As a result, the 2016 Credit Agreement will mature in January 2022. At our option, amounts borrowed under the 2016 Credit Agreement will bear interest at either the LIBOR rate or a fluctuating base rate, in each case, plus an applicable margin determined on a quarterly basis based on our consolidated ratio of total indebtedness to EBITDA (as calculated in accordance with the 2016 Credit Agreement). The 2016 Credit Agreement contains customary events of default and customary affirmative and negative covenants. As of December 31, 2016, we were in compliance with such covenants and we had not drawn any amounts. Lung Biotechnology PBC is our only subsidiary that guarantees our obligations under the 2016 Credit Agreement though, from time to time, one or more of our other subsidiaries may be required to guarantee such obligations. Secured Line of Credit In September 2013, we entered into a one-year credit agreement (the 2013 Credit Agreement) with Wells Fargo for a $75.0 million revolving loan facility. In each of July 2014 and July 2015, we amended the 2013 Credit Agreement solely to extend its maturity to September 30 of 2015 and 2017, respectively. In January 2016, we terminated and repaid in full all obligations under the 2013 Credit Agreement when we entered into the 2016 Credit Agreement. Convertible Notes Due 2016 In October 2011, we issued $250.0 million in aggregate principal value 1.0 percent Convertible Senior Notes due September 15, 2016 (Convertible Notes). Upon maturity of the Convertible Notes on September 15, 2016, we fulfilled all remaining settlement and repayment obligations. The Convertible Notes were unsecured, unsubordinated debt obligations that ranked equally with all of our other unsecured and unsubordinated indebtedness. We paid interest semi-annually on March 15 and September 15 of each year. The initial conversion price was $47.69 per share and the number of underlying shares used to determine the aggregate consideration upon conversion was approximately 5.2 million shares. Upon conversion, holders of our Convertible Notes were entitled to receive: (1) cash equal to the lesser of the par value of the notes or the conversion value (the number of shares underlying the Convertible Notes multiplied by the then current conversion price per share); and (2) to the extent the conversion value exceeded the par value of the notes, shares of our common stock. During the year ended December 31, 2016, we settled conversion requests representing $5.6 million in principal value of our Convertible Notes. We paid $5.6 million in principal and issued 0.1 million shares of our common stock during the settlement process. We received 0.1 million shares of our common stock under our convertible note hedge (discussed below under Convertible Note Hedge and Warrant Transactions) from Deutsche Bank AG London (DB London) which we placed into our treasury stock account. Convertible Note Hedge and Warrant Transactions In connection with the issuance of our Convertible Notes, we entered into separate convertible note hedge and warrant transactions with DB London to reduce the potentially dilutive impact of the conversion of our convertible notes. Pursuant to the convertible note hedge, we purchased call options to acquire up to approximately 5.2 million shares of our common stock with a strike price of $47.69. The call options became exercisable upon any conversions and the maturity of the Convertible Notes, and terminated upon the maturity of the Convertible Notes. The call options offset on a share for share basis, any shares of our common stock that we issued upon any conversion of our Convertible Notes. We also sold DB London warrants to acquire up to approximately 5.2 million shares of our common stock with a strike price of $67.56. The warrants expired incrementally on a series of expiration dates that began in December 2016 and ended in January 2017. The warrants were settled on a net-share basis. As the price of our common stock exceeded the strike price of the warrants on the series of related incremental expiration dates, we issued 2.8 million shares of our common stock to DB London during the term of the warrant, of which, 1.1 million shares were issued during 2016. Interest Expense Details of interest expense presented on our consolidated statements of operations are as follows (in millions): Year Ended 2016 2015 2014 Contractual coupon rate of interest—convertible notes $ — $ $ Discount amortization—convertible notes ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest expense—convertible notes Other interest expense (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total interest expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Represents interest expense related to debt and amortization of issuance costs.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Commitments and Contingencies	9. Commitments and Contingencies Operating Leases We lease facilities and equipment under operating lease arrangements that have terms expiring at various dates through 2020. Certain lease arrangements include renewal options and escalation clauses. In addition, various lease agreements to which we are party require that we comply with certain customary covenants throughout the term of these leases. If we are unable to comply with these covenants and cannot reach a satisfactory resolution in the event of noncompliance, these agreements could terminate. Future minimum lease payments under non-cancelable operating leases as of December 31, 2016, are as follows (in millions): Year Ending December 31, 2017 $ 2018 2019 2020 ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total rent expense was $4.4 million, $3.8 million and $3.6 million for the years ended December 31, 2016, 2015 and 2014, respectively. Milestone Payments We are party to certain license agreements as described in Note 15—Assignment and License Agreements and acquisition agreements. Generally, these agreements require that we make milestone payments in cash upon the achievement of certain product development and commercialization goals and payments of royalties upon commercial sales. Future milestone payments based on our estimates of the timing and probability of achieving milestones specified under these arrangements are as follows (in millions): Year Ending December 31, (1) 2017 $ 2018 2019 2020 2021 Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) The amounts and timing of future milestone payments may vary depending on when related milestones will be attained, if at all.

Temporary Equity

Temporary Equity	12 Months Ended
	Dec. 31, 2016
Temporary Equity
Temporary Equity	10. Temporary Equity Temporary equity includes securities that: (1) have redemption features that are outside our control; (2) are not classified as an asset or liability; (3) are excluded from permanent stockholders' equity; and (4) are not mandatorily redeemable. Amounts included in temporary equity relate to securities that are redeemable at a fixed or determinable price. Components comprising the carrying value of temporary equity include the following (in millions): As of 2016 2015 Reclassification of Equity Component (1) $ — $ Common stock subject to repurchase (2) ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Represents the reclassification of the Equity Component equal to the unamortized debt discount of our Convertible Notes as of December 31, 2015 from additional paid-in capital to temporary equity. Our Convertible Notes were convertible at the election of the holders as noted in Note 8— Debt — Convertible Notes Due 2016 . The Convertible Notes matured in September 2016. (2) In connection with our license agreement with Toray Industries Inc. (Toray), we issued 200,000 shares of our common stock (which have since split into 400,000 shares) to Toray in 2007, and provided Toray the right to require us to repurchase the shares at a price of $27.21 per share.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity
Stockholders' Equity	11. Stockholders' Equity Earnings Per Common Share Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period, adjusted for the potential dilutive effect of other securities if such securities were converted or exercised. The components of basic and diluted earnings per share comprised the following (in millions, except per share amounts): Year Ended December 31, 2016 2015 2014 Numerator: Net income $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted average outstanding shares—basic Effect of dilutive securities (1) : Convertible notes — Warrants Stock options, restricted stock units and employee stock purchase plan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares—diluted (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per common share: Basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options and warrants excluded from calculation (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Calculated using the treasury stock method. (2) Certain convertible notes, stock options and warrants have been excluded from the computation of diluted earnings per share because their impact would be anti-dilutive. Under our convertible note hedge agreement, we were entitled to receive shares required to be issued to investors upon conversion of our Convertible Notes. Since related shares used to compute dilutive earnings per share would be anti-dilutive, they have been excluded from the calculation above. Equity Incentive Plans As of December 31, 2016, we have two shareholder-approved equity incentive plans: the United Therapeutics Corporation Amended and Restated Equity Incentive Plan (the 1999 Plan) and the United Therapeutics Corporation 2015 Stock Incentive Plan (the 2015 Plan). The 2015 Plan was approved by our shareholders in June 2015 and provides for the issuance of up to 6,150,000 shares of our common stock pursuant to awards granted under the 2015 Plan. As a result of the approval of the 2015 Plan, no further awards will be granted under the 1999 Plan. During the years ended December 31, 2016 and December 31, 2015, we granted 1.6 million and 0.2 million stock options under the 2015 Plan, respectively. Employee Stock Options We estimate the fair value of stock options using the Black-Scholes-Merton valuation model. Option-pricing models, including the Black-Scholes-Merton model, require the use of judgment and subjective assumptions that can materially impact the estimation of fair value and share-based compensation. Share-based compensation expense is recorded ratably over the vesting period of the stock option. Inputs included in estimating the fair value of a stock option include the price of our common stock, the expected volatility of our common stock, the risk-free interest rate, the expected term of stock option awards, the expected forfeiture rate and the expected dividend yield. A description of the key inputs, requiring estimates, used in determining the fair value of stock options is provided below: Expected volatility —Volatility is a measure of the amount the price of our common stock has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. We use historical volatility based on weekly price observations of our common stock during the period immediately preceding a stock option grant that is equal to the expected term of the grant (up to a maximum of five years). We believe the volatility of the price of our common stock measured over the preceding five years provides a reliable projection of future long-term volatility. Risk-free interest rate —The risk-free interest rate is the average interest rate consistent with the yield available on a U.S. Treasury note with a term equal to the expected term of a given stock option grant. Expected term —The expected term reflects the estimated time period we expect an option grant to remain outstanding. We use historical data to develop this input. Expected forfeiture rate —The expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis prior to becoming fully vested. We derive our estimate based on historical forfeiture experience for similar classes of employees. Expected dividend yield —We do not pay dividends on our common stock and do not expect to do so in the future. Therefore, the dividend yield is assumed to be zero. The following weighted-average assumptions were used in estimating the fair value of stock options granted to employees: Year Ended 2016 2015 2014 Expected volatility % % % Risk-free interest rate % % % Expected term of options (in years) Expected forfeiture rate (1) % % % Expected dividend yield % % % (1) During 2016 we issued stock options to all employees, which resulted in an increase in the forfeiture rate compared to prior years. A summary of the status and activity of stock options is presented below: Options Weighted- Weighted Aggregate Outstanding at January 1, 2016 $ Granted Exercised ) Forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The weighted average fair value of a stock option granted during each of the years in the three-year period ended December 31, 2016, was $42.59, $60.70 and $40.70, respectively. The total fair value of stock options that vested for each of the years in the three-year period ended December 31, 2016, was $19.9 million, $0.0 million and $29.5 million, respectively. Total share-based compensation expense relating to stock options is as follows (in millions): Year Ended December 31, 2016 2015 2014 Cost of product sales $ $ — $ — Research and development — — Selling, general and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense before tax Related income tax benefit ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense, net of tax $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Selling, general and administrative expense for the year ended December 31, 2016 includes approximately $9.8 million of costs related to the accelerated vesting of stock options associated with the departure of a corporate officer during the second quarter of 2016. As of December 31, 2016, the unrecognized compensation cost was $39.2 million. Unvested outstanding stock options as of December 31, 2016 had a weighted average remaining vesting period of 3.2 years. Stock option exercise data is summarized below (dollars in millions): Year Ended December 31, 2016 2015 2014 Number of options exercised Cash received from options exercised $ $ $ Total intrinsic value of options exercised $ $ $ Tax benefits realized from options exercised $ $ $ Restricted Stock Units In June 2016, we began issuing restricted stock units under the 2015 Plan to non-employee directors. Each restricted stock unit entitles the director to receive one share of our common stock upon vesting, subject to the director's election to defer receipt of shares to a later date. We measure the fair value of restricted stock units using the stock price on the date of grant. During the year ended December 31, 2016, we granted 20,960 restricted stock units under the 2015 Plan with a weighted average grant date fair value of $101.80. The restricted stock units have an aggregate grant date fair value of $2.1 million. Share-based compensation expense is recorded ratably over the vesting period of the restricted stock unit. We recorded $1.1 million in share-based compensation expense for the year ended December 31, 2016 related to restricted stock units. The share-based compensation expense related to restricted stock units granted is reflected in selling, general and administrative expense on the statements of operations. As of December 31, 2016, unrecognized compensation cost related to the grant of restricted stock units was $1.0 million. Unvested outstanding restricted stock units as of December 31, 2016 had a weighted average remaining vesting period of 0.5 years. Employee Stock Purchase Plan In June 2012, our shareholders approved the United Therapeutics Corporation Employee Stock Purchase Plan (ESPP), which has been structured to comply with Section 423 of the Internal Revenue Code. The ESPP provides eligible employees with the right to purchase shares of our common stock at a discount through elective accumulated payroll deductions at the end of each offering period. Offering periods, which began in September 2012, occur in consecutive six-month periods commencing on September 5th and March 5th of each year. Eligible employees may contribute up to 15 percent of their base salary, subject to certain annual limitations as defined in the ESPP. The purchase price of the shares is equal to the lower of 85 percent of the closing price of our common stock on either the first or last trading day of a given offering period. In addition, the ESPP provides that no eligible employee may purchase more than 4,000 shares during any offering period. The ESPP has a 20-year term and limits the aggregate number of shares that can be issued under the ESPP to 3.0 million. Share Repurchases In June 2014, our Board of Directors authorized the repurchase of up to $500.0 million of our common stock. This program became effective on August 1, 2014, and remained open for one year. During the years ended December 31, 2015, and 2014, we repurchased approximately 2.4 million and 0.9 million shares of our common stock, respectively, at an aggregate cost of $394.5 million and $105.5 million, respectively, under this repurchase program. We completed this repurchase program in September 2015. In October 2015, our Board of Directors authorized a new program for the repurchase of up to $500.0 million of our common stock in open or privately negotiated transactions, at our discretion. This program was effective from January 1, 2016 through December 31, 2016. During the year ended December 31, 2016, we repurchased approximately 4.2 million shares of our common stock at an aggregate cost of $500.0 million. Shareholder Rights Plan In June 2008, we entered into an Amended and Restated Rights Agreement with The Bank of New York as Rights Agent (the Plan), which amended and restated our original Rights Agreement dated December 17, 2000. The Plan, as amended and restated, extended the expiration date of the Preferred Share Purchase Rights (Rights) from December 29, 2010 to June 26, 2018, and increased the purchase price of each Right from $64.75 to $400.00, respectively. Each Right entitles holders to purchase one one-thousandth of a share of our Series A Junior Participating Preferred Stock. Rights are exercisable only upon our acquisition by another company, or commencement of a tender offer that would result in ownership of 15 percent or more of the outstanding shares of our voting stock by a person or group (as defined under the Plan) without our prior express written consent. As of December 31, 2016, we have not issued any shares of our Series A Preferred Stock.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2016
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss	12. Accumulated Other Comprehensive Loss The following table includes changes in accumulated other comprehensive loss by component, net of tax (in millions): Defined Benefit (1) Foreign Currency (2) Total Balance, January 1, 2016 $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) Amounts reclassified from accumulated other comprehensive loss — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive income (loss) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, December 31, 2016 $ $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Defined Benefit (1) Foreign Currency Total Balance, January 1, 2015 $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) ) Amounts reclassified from accumulated other comprehensive loss — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive income (loss) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, December 31, 2015 $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Refer to Note 14— Employee Benefit Plans — Supplemental Executive Retirement Plan , which identifies the captions within our consolidated statement of operations where reclassification adjustments were recognized and their associated tax impact. (2) In the fourth quarter of 2016, we changed the functional currency for our foreign entities to the U.S. dollar. The loss on foreign currency translation attributable to each foreign entity at the time of this change will remain in accumulated other comprehensive loss until the sale or substantial liquidation of the foreign entity.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Taxes
Income Taxes	13. Income Taxes Components of income tax expense (benefit) consist of the following (in millions): Year Ended December 31, 2016 2015 2014 Current: Federal $ $ $ State ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total current Deferred Federal ) ) State ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total deferred ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Presented below is a reconciliation of income tax expense computed at the statutory federal tax rate to income tax expense as reported (in millions): Year Ended December 31, 2016 2015 2014 Federal taxes at 35% $ $ $ State taxes, net of federal benefit General business credits ) ) ) Section 199 deduction ) ) ) Nondeductible compensation expense ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Components of the net deferred tax assets are as follows (in millions): As of 2016 2015 Deferred tax assets: Intangible assets $ $ Nonqualified stock options SERP STAP awards Other ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets Deferred tax liabilities: Plant and equipment principally due to differences in depreciation ) ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets before valuation allowance Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ We do not provide for U.S. income taxes on undistributed earnings of our foreign operations that are intended to be invested indefinitely outside the United States. At December 31, 2016, the cumulative amount of undistributed foreign earnings was approximately $13 million. If these earnings were repatriated to the United States, we would be subject to U.S. income taxes (after application of foreign tax credits). It is not practicable to estimate the tax cost of repatriating the cumulative undistributed taxable earnings of these foreign subsidiaries to the United States. A reconciliation of the beginning and ending balances of unrecognized tax benefits is as follows (in millions): As of 2016 2015 Unrecognized tax benefits at the beginning of year $ $ Lapse of statute of limitations — ) ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized tax benefits at the end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized tax benefits at both December 31, 2016 and 2015, included $0.3 million of tax benefits that, if recognized, would impact our effective tax rate. We record interest and penalties related to uncertain tax positions as a component of income tax expense. As of both December 31, 2016 and 2015, we have not accrued any interest expense relating to uncertain tax positions. We are unaware of any positions for which it is reasonably possible that the total amount of unrecognized tax benefits will significantly increase or decrease within the next twelve months. We are subject to federal and state taxation in the United States and various foreign jurisdictions. We are no longer subject to income tax examinations by the Internal Revenue Service and substantially all other major jurisdictions for tax years prior to 2011. At December 31, 2016, we had no federal net operating loss carryforwards and approximately $55 million of state net operating loss carryforwards which will expire at various dates between the years 2028 and 2036, if not utilized.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2016
Employee Benefit Plans
Employee Benefit Plans	14. Employee Benefit Plans Supplemental Executive Retirement Plan We maintain the United Therapeutics Corporation Supplemental Executive Retirement Plan (SERP) to provide retirement benefits to certain senior members of our management team. Participants who retire at age 60 or older are eligible to receive either monthly payments or a lump sum payment based on an average of their total gross base salary over the last 36 months of active employment, subject to certain adjustments. Related benefit payments commence on the first day of the sixth month after retirement. Participants who elect to receive monthly payments will continue payments through the remainder of their life. Alternatively, participants who elect to receive a lump sum distribution will receive a payment equal to the present value of the estimated monthly payments that would have been received upon retirement. As of December 31, 2016 and 2015, all SERP participants had elected to receive a lump sum distribution. Participants who terminate employment for any reason other than death, disability, or change in control prior to age 60 will not be entitled to receive any benefits under the SERP. We recognize the unfunded balance of the SERP as a liability on our consolidated balance sheets. Since we do not fund the SERP, the liability is equal to the projected benefit obligation as measured at the end of each fiscal year. Expenses related to the SERP are reported under the captions, "Research and development expense" and "Selling, general and administrative expense" in the accompanying consolidated statements of operations. A reconciliation of the beginning and ending balances of the projected benefit obligation is presented below (in millions): Year Ended 2016 2015 Projected benefit obligation at the beginning of the year $ $ Service cost Interest cost Plan amendments — Benefits paid — ) Actuarial gain (1) ) ) ​ ​ ​ ​ ​ ​ ​ ​ Projected benefit obligation at the end of the year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets at the end of the year — — ​ ​ ​ ​ ​ ​ ​ ​ Unfunded at end of the year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount included in Other current liabilities (2) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) During the second quarter of 2016, certain participants in the SERP departed before retirement age under the terms of the SERP. As a result, we remeasured the benefit obligation under the SERP as of June 30, 2016, and recorded a reduction to the benefit obligation with a corresponding increase to "Actuarial gain arising during period, net of tax" within "Accumulated other comprehensive loss" of $7.1 million. As part of the re-measurement of the benefit obligation, we updated the discount rate we used to measure our SERP obligation to 3.36 percent. The discount rate as of December 31, 2015 was 3.82 percent. (2) The amount included under the caption "Other current liabilities" on our consolidated balance sheet represents the benefit obligation due to participants who are eligible to retire. The accumulated benefit obligation, a measure that does not consider future increases in participants' salaries, was $37.5 million and $42.3 million at December 31, 2016 and 2015, respectively. Future estimated benefit payments, based on current assumptions, including election of lump-sum distributions and expected future service, are as follows (in millions): Year Ended December 31, 2017 $ 2018 — 2019 2020 — 2021 — Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following weighted-average assumptions were used to measure the SERP obligation: Year Ended 2016 2015 Discount Rate % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salary Increases % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The components of net periodic pension cost recognized on our consolidated statements of operations consist of the following (in millions): Year Ended 2016 2015 2014 Service cost $ $ $ Interest cost Amortization of prior service cost Amortization of net actuarial (gain) loss ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reclassification adjustments related to the SERP from accumulated other comprehensive loss to the statements of operations by line item and the tax impact of these reclassifications is presented below (in millions): Components Reclassified from Accumulated Other Comprehensive Loss (1) As of As of Prior service cost: Research and development $ $ Selling, general and administrative ​ ​ ​ ​ ​ ​ ​ ​ Total Amortization of net actuarial (gain) loss: Research and development ) — Selling, general and administrative ) ​ ​ ​ ​ ​ ​ ​ ​ Total ) Total prior service cost and amortization of net actuarial (gain) loss Tax benefit ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Refer to Note 12— Accumulated Other Comprehensive Loss . Amounts relating to the SERP that have been recognized in other comprehensive income (loss) are as follows (in millions): Year Ended 2016 2015 2014 Net unrecognized actuarial gain $ $ $ Net unrecognized prior service (benefit) cost ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Tax benefit ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The table below presents amounts relating to the SERP included in accumulated other comprehensive loss that have not yet been recognized as a component of net periodic pension cost on our consolidated statements of operations (in millions): Year Ended 2016 2015 2014 Net unrecognized actuarial (gain) loss $ ) $ $ Net unrecognized prior service cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ) Tax expense (benefit) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Estimated amounts included in accumulated other comprehensive loss as of December 31, 2016, that are expected to be recognized as components of net periodic pension cost on our statements of operations for the year ended December 31, 2017, comprise the following (in millions): Amortization of prior service cost $ Amortization of net actuarial gain ) ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Retirement Plan We maintain a Section 401(k) Salary Reduction Plan which is open to all eligible full-time employees. Under the 401(k) Plan, eligible employees can make pre-tax contributions up to statutory limits. Currently, we make discretionary matching contributions to the 401(k) Plan equal to 40 percent of a participant's elected salary deferral. Matching contributions vest immediately for participants who have been employed for three years; otherwise, matching contributions vest annually, in one-third increments over a three-year period until the three-year employment requirement has been met.

Assignment and License Agreemen

Assignment and License Agreements	12 Months Ended
	Dec. 31, 2016
Assignment and License Agreements
Assignment and License Agreements	15. Assignment and License Agreements GlaxoSmithKline plc In 1997, GlaxoSmithKline plc (Glaxo) assigned to us patents and patent applications covering treprostinil for the treatment of PAH and congestive heart failure. Under the agreement, Glaxo was entitled to receive royalties on sales exceeding a specified threshold for a minimum period of ten years (or until expiration of the licensed patents) following the date of the first commercial sale of any initial product containing treprostinil. Pursuant to these terms, our royalty obligation ended in October 2014. Supernus Pharmaceuticals, Inc. In June 2006, we entered into an exclusive license agreement with Supernus Pharmaceuticals, Inc. (Supernus) for the use of certain technologies developed by Supernus in our Orenitram tablet. Under this agreement, we paid Supernus certain amounts upon the achievement of specified milestones based on the development and commercial launch of Orenitram for PAH, and we would be obligated to make additional milestone payments if we develop Orenitram for a second indication. Additionally, we pay a single digit royalty under this agreement, based on net product sales of Orenitram. Royalties will be paid for approximately twelve years commencing with the first commercial sale, which occurred in the second quarter of 2014. Eli Lilly and Company In November 2008, we acquired from Lilly exclusive rights to develop, market, promote and commercialize Adcirca for the treatment of pulmonary hypertension in the United States. In exchange for these license rights, we agreed to pay Lilly, among other fees, royalties of five percent of our net product sales of Adcirca as a pass through of Lilly's third-party royalty obligations for as long as Lilly is required to make such royalty payments. Pursuant to the terms of our license arrangement, Lilly manufactures Adcirca for us and distributes Adcirca via its wholesaler network in the same manner that it distributes its own pharmaceutical products. We purchase Adcirca from Lilly at a fixed manufacturing cost, which is adjusted by Lilly from time to time. The terms of this licensing arrangement will continue generally until the later of: (1) the expiration or lapse of the last to expire claim within a Lilly patent covering commercialization of Adcirca; or (2) the expiration of any government conferred exclusivity rights to Adcirca. In addition, at Lilly's discretion the license agreement may be terminated in the event that we undergo a change in control. National Cancer Institute and The Scripps Research Institute In July 2010, we entered into a Cooperative Research and Development Agreement (CRADA) with the National Cancer Institute (NCI) of the United States National Institutes for Health (NIH) to collaborate on the late-stage development and regulatory approval process for Unituxin for children with high-risk neuroblastoma and patients with other forms of cancer. In lieu of a royalty payment to the NCI, we have an obligation to provide the NCI with Unituxin for certain of its studies free of charge. Under a non-exclusive license agreement with The Scripps Research Institute, we pay a royalty of one percent of Unituxin's net sales. Toray Industries, Inc. In 2000, we entered into an agreement with Toray to obtain exclusive rights to develop and market beraprost, a chemically stable oral prostacyclin analogue, in a sustained release formulation in the United States and Canada for the treatment of all cardiovascular indications. In 2007, we amended the agreement to expand our rights to commercialize modified release formulations of beraprost, which include esuberaprost. As part of the 2007 amendment, we issued 200,000 shares of our common stock (which have since split into 400,000 shares) to Toray with certain put rights. These put rights provide Toray the ability to request at its discretion that we repurchase these shares at a price of $27.21 per share upon 30 days' prior written notice. Accordingly, we classified the value of the shares within temporary equity on our consolidated balance sheets. In the event that Toray requests that we repurchase these shares, we will reclassify the repurchase value of the stock as a liability until settlement. The 2007 amendment also provided for certain milestone payments during the development period and upon receipt of regulatory approval in the United States or the European Union. In July 2011, we amended our license agreement with Toray. The amendment did not materially change the terms of our license agreement, except for a reduction in royalty rates in exchange for a total of $50.0 million in equal, non-refundable payments to Toray over the five-year period ending in 2015. As of December 31, 2015, we have fulfilled this obligation to Toray. Medtronic Inc. In 2009, we entered into an agreement with Medtronic, Inc. (Medtronic) providing us exclusive rights in the United States and certain other countries to develop Medtronic's proprietary intravascular infusion catheter to be used with its SynchroMed ® II implantable infusion pump and related infusion system components (together referred to as the Implantable System for Remodulin) in order to deliver Remodulin for the treatment of PAH. If this development program is successful, our agreement provides that, upon commercialization, we will purchase infusion pumps and supplies from Medtronic and will also pay a ten percent royalty to Medtronic based on net product sales of Remodulin for use in the Implantable System for Remodulin within the exclusive territories, subject to certain adjustments specified in the agreement. The Implantable System for Remodulin will be exclusive to Remodulin so long as we purchase a minimum percentage of our annual requirement for implantable pump systems from Medtronic. We will be solely responsible for all marketing and promotion of the Implantable System for Remodulin for the treatment of PAH in the exclusive territories. DEKA Research & Development Corp. In December 2014, we entered into an exclusive agreement with DEKA Research & Development Corp. (DEKA) to develop a pre-filled, semi-disposable pump system for subcutaneous delivery of Remodulin. Under the terms of the agreement, we will fund the development costs related to the semi-disposable pump system and will pay product fees and a single-digit royalty to DEKA based on commercial sales of the system and the Remodulin sold for use with the system. Other We are party to various other license agreements relating to therapies under development. These license agreements require us to make payments based on a percentage of sales, if we are successful in commercially developing these therapies, and may require other payments upon the achievement of certain milestones.

Distribution Agreements

Distribution Agreements	12 Months Ended
	Dec. 31, 2016
Distribution Agreements
Distribution Agreements	16. Distribution Agreements U.S.-Based Specialty Distributors We are party to separate distribution agreements for Remodulin, Tyvaso and Orenitram with two U.S.-based specialty pharmaceutical distributors, Accredo and CVS Caremark. The distribution agreements are similar to one another, and generally have one-year terms that renew automatically for additional one-year periods, unless terminated earlier. The agreements contain contractual responsibilities relating to ordering specifications, inventory requirements and exchange rights. We also have agreements with these distributors to perform certain services for us on a fee-for-service basis. If any of our distribution agreements expire or terminate, we may be required under certain circumstances to repurchase any unsold inventory held by our distributors. In the second quarter of 2015, we entered into an exclusive distribution agreement with ASD Specialty Healthcare, Inc. (ASD), an affiliate of AmerisourceBergen Corporation, to distribute Unituxin in the United States. Under this Agreement, we sell Unituxin to ASD at a transfer price that we establish, and we pay ASD fees for services provided in connection with the distribution and support of Unituxin. International Distributors We currently sell Remodulin, Tyvaso and Unituxin internationally through various distributors. The financial terms and conditions relating to these distributor arrangements are generally structured in a manner substantially similar to those of our U.S. distribution agreements described above.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
Segment Information
Segment Information	17. Segment Information We currently operate as one operating segment with a focus on the development and commercialization of products to address the unmet needs of patients with chronic and life-threatening conditions. Our Chief Executive Officer, as our chief operating decision maker, manages and allocates resources to the operations of our company on a consolidated basis. This enables our Chief Executive Officer to assess the overall level of resources available and how to best deploy these resources across functions, therapeutic areas, and research and development projects that are in line with our long-term company-wide strategic goals. Net product sales, cost of product sales and gross profit for each of our commercial products were as follows (in millions): Remodulin Tyvaso Adcirca Orenitram Unituxin Total Year Ended December 31, 2016 Net product sales $ $ $ $ $ $ Cost of product sales ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2015 (1) Net product sales $ $ $ $ $ $ Cost of product sales ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2014 (2) Net product sales $ $ $ $ $ — $ Cost of product sales — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) We commenced sales of Unituxin during the third quarter of 2015. (2) We commenced sales of Orenitram during the second quarter of 2014. Geographic revenues are determined based on the country in which our customers (distributors) are located. Total revenues from external customers by geographic area are as follows (in millions): Year Ended December 31, 2016 2015 2014 United States $ $ $ Rest-of-World (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (2) $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Primarily Europe. (2) Total includes other revenue of $5.2 million and $9.0 million for the years ended December 31, 2015 and 2014, respectively. We recorded revenue from two specialty pharmaceutical distributors comprising 50 percent and 14 percent of total revenues in 2016, 55 percent and 16 percent of total revenues in 2015, and 58 percent and 15 percent of total revenues in 2014, respectively. All of our revenues for Adcirca are distributed through Lilly's pharmaceutical wholesaler network. Long-lived assets (property, plant and equipment) located by geographic area are as follows (in millions): Year Ended December 31, 2016 2015 2014 United States $ $ $ Rest-of-World ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information (Unaudited)
Quarterly Financial Information (Unaudited)	18. Quarterly Financial Information (Unaudited) Summarized quarterly financial information for each of the years ended December 31, 2016 and 2015 are as follows (in millions, except per share amounts): Quarter Ended December 31, September 30, June 30, March 31, Total revenues $ $ $ $ Cost of product sales Gross profit Net income (1) Net income per share—basic $ $ $ $ Net income per share—diluted $ $ $ $ Quarter Ended December 31, September 30, June 30, March 31, Total revenues $ $ $ $ Cost of product sales Gross profit Net income (loss) (2)(3) ) Net income (loss) per share—basic $ $ $ $ ) Net income (loss) per share—diluted $ $ $ $ ) (1) Operating results for the quarter ended December 31, 2016, September 30, 2016, June 30, 2016 and March 31, 2016 include $64.2 million, $28.7 million, $(7.0) million and $(95.5) million net of tax expense (benefit) to operating expenses for STAP related share-based compensation expense, respectively. (2) Operating results for the quarter ended December 31, 2015, September 30, 2015, June 30, 2015 and March 31, 2015 include $73.9 million, $(75.7) million, $27.5 million and $145.0 million net of tax expense (benefit) to operating expenses for STAP related share-based compensation expense, respectively. (3) Operating results for the quarter ended September 30, 2015, include a gain on sale of the PPRV we received from the FDA in connection with the approval of Unituxin, for $350.0 million in cash. The proceeds from the sale of the PPRV were recognized as a gain on the sale of an intangible asset, as the PPRV did not have a carrying value on our consolidated balance sheet at the time of sale.

Litigation

Litigation	12 Months Ended
	Dec. 31, 2016
Litigation
Litigation	19. Litigation Watson Laboratories, Inc. In June 2015, we received a Paragraph IV certification notice letter from Watson Laboratories, Inc. (Watson) indicating that Watson has submitted an abbreviated new drug application (ANDA) to the FDA to market a generic version of Tyvaso. In its notice letter, Watson states that it intends to market a generic version of Tyvaso before the expiration of U.S. Patent Nos. 6,521,212 and 6,756,033, each of which expires in November 2018; and U.S. Patent No. 8,497,393, which expires in December 2028. Watson's notice letter states that the ANDA contains a Paragraph IV certification alleging that these patents are not valid, not enforceable, and/or will not be infringed by the commercial manufacture, use or sale of the proposed product described in Watson's ANDA submission. We responded to the Watson notice letter by filing a lawsuit on July 22, 2015 against Watson in the U.S. District Court for the District of New Jersey alleging infringement of U.S. Patent Nos. 6,521,212, 6,756,033, and 8,497,393. Under the Hatch-Waxman Act, the FDA is automatically precluded from approving Watson's ANDA for up to 30 months from receipt of Watson's notice letter or until the issuance of a U.S. District Court decision that is adverse to us, whichever occurs first. In September 2015, Watson filed (1) a motion to dismiss some, but not all, counts of the complaint; (2) its answer to the complaint; and (3) certain counterclaims against us. The Court granted Watson's motion to dismiss certain counts of our complaint. In September 2015, we filed our answer to Watson's counterclaims. In June 2016, Watson sent a second Paragraph IV certification notice letter addressing two new patents, U.S. Patent Nos. 9,339,507 and 9,358,240. In June 2016, we filed an amended complaint against Watson asserting these two additional patents. The parties are currently engaged in discovery, and trial on all of the asserted patents is currently scheduled to take place in September 2017. We intend to vigorously enforce our intellectual property rights relating to Tyvaso. Actavis Laboratories FL, Inc. In February 2016, we received a Paragraph IV certification notice letter (the First Actavis Notice Letter) from Actavis Laboratories FL, Inc. (Actavis) indicating that Actavis has submitted an ANDA to the FDA to market a generic version of the 2.5 mg strength of Orenitram. The First Actavis Notice Letter states that Actavis intends to market a generic version of the 2.5 mg strength of Orenitram before the expiration of the following patents, all of which are listed in the Orange Book: U.S. Patent No. Expiration Date 8,252,839 May 2024 9,050,311 May 2024 7,544,713 July 2024 7,417,070 July 2026 8,497,393 December 2028 8,747,897 October 2029 8,410,169 February 2030 8,349,892 January 2031 The First Actavis Notice Letter states that the ANDA contains a Paragraph IV certification alleging that these patents are not valid, not enforceable, and/or will not be infringed by the commercial manufacture, use or sale of the proposed product described in Actavis' ANDA submission. We responded to the First Actavis Notice Letter by filing a lawsuit (the First Actavis Action) against Actavis in March 2016 in the U.S. District Court for the District of New Jersey alleging infringement of each of the patents noted above and one additional patent, U.S. Patent No. 9,278,901 (the '901 patent), which expires in May 2024 and is also now listed in the Orange Book. Under the Hatch-Waxman Act, the FDA is automatically precluded from approving Actavis' ANDA with respect to the 2.5 mg strength of Orenitram for up to 30 months from receipt of Actavis' notice letter or until the issuance of a U.S. District Court decision that is adverse to us with respect to all of the eight patents listed in the table above, whichever occurs first. In June 2016, we filed an amended complaint against Actavis, Actavis filed its answer and counterclaims to that amended complaint, and we filed our answer to those counterclaims. In May 2016, we received a second Paragraph IV certification notice letter from Actavis (the Second Actavis Notice Letter) indicating that Actavis has amended its ANDA to include its generic version of the 0.25 mg and 1.0 mg strengths of Orenitram, in addition to the 2.5 mg strength identified in the First Actavis Notice Letter. We responded to the Second Actavis Notice Letter by filing an additional lawsuit against Actavis (the Second Actavis Action) on June 17, 2016 in the U.S. District Court for the District of New Jersey alleging infringement of the same patents asserted in the First Actavis Action. The Second Actavis Action triggered an additional 30-month stay with respect to the 0.25 mg and 1.0 mg strengths. Specifically, the FDA is automatically precluded from approving Actavis' ANDA with respect to the 0.25 mg and 1.0 mg strengths of Orenitram for up to 30 months from receipt of the Second Actavis Notice Letter or until the issuance of a U.S. District Court decision that is adverse to us with respect to all of the eight patents listed in the table above and the '901 patent, whichever occurs first. The Court has consolidated the First Actavis Action and the Second Actavis Action. The parties are currently engaged in discovery, and trial is scheduled for February 2018. We intend to vigorously enforce our intellectual property rights relating to Orenitram. SteadyMed Ltd. On October 1, 2015, SteadyMed Ltd. (SteadyMed) filed a petition with the Patent Trial and Appeal Board (PTAB) of the U.S. Patent and Trademark Office for inter partes review (the IPR Petition) of U.S. Patent No. 8,497,393 (the '393 Patent), which is owned by United Therapeutics. In its IPR Petition, SteadyMed seeks to invalidate '393 Patent, which expires in December 2028 and covers a method of making treprostinil, the active pharmaceutical ingredient in our Remodulin, Tyvaso and Orenitram products. The '393 Patent was also the subject of now-settled litigation with generic companies relating to ANDAs to market generic versions of Remodulin, and remains the subject of our pending litigation with Watson and Actavis, described above. The PTAB granted the petition for review, and subsequently, the parties made a number of submissions to the PTAB with their supporting evidence and arguments. Oral argument was held in November 2016. We are currently awaiting the PTAB's final decision, which we expect in or before April 2017. SteadyMed has announced that it is developing a product called Trevyent™, which is a single-use, pre-filled pump for which it plans to seek FDA approval for delivery of a two-day supply of treprostinil subcutaneously using its PatchPump® technology. Department of Justice Subpoena In May 2016, we received a subpoena from the U.S. Department of Justice requesting documents regarding our support of 501(c)(3) organizations that provide financial assistance to patients taking our medicines. Other companies have received similar inquiries. We are cooperating with this inquiry.

Schedule II-Valuation and Quali

Schedule II-Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Schedule II-Valuation and Qualifying Accounts
Schedule II-Valuation and Qualifying Accounts	Schedule II—Valuation and Qualifying Accounts Valuation Allowance on Deferred Tax Assets Balance at Additions Deductions Balance at Year Ended December 31, 2016 $ $ $ — $ Year Ended December 31, 2015 $ $ $ — $ Year Ended December 31, 2014 $ $ $ — $ Reserve for Inventory Obsolescence Balance at Additions Deductions Balance at Year Ended December 31, 2016 $ $ $ ) $ Year Ended December 31, 2015 $ $ $ ) $ Year Ended December 31, 2014 $ $ $ ) $

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements of United Therapeutics Corporation and its wholly owned subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States (GAAP). All intercompany balances and transactions have been eliminated in consolidation. In the current liabilities section of our balance sheet, we reclassified the prior period amount within "convertible notes" to "other current liabilities" to conform with the current period presentation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We base our estimates on assumptions regarding historical experience, currently available information and anticipated developments that we believe are reasonable and appropriate. However, because the use of estimates involves an inherent degree of uncertainty, actual results could differ from those estimates. Our significant accounting policies that require use of subjective and/or complex judgment and estimates impact the following financial statement areas: revenue recognition, share-based compensation, marketable investments, fair value measurements (including those relating to our acquisitions), income taxes, goodwill and other intangible assets, and obligations related to our Supplemental Executive Retirement Plan.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses approximate fair value because of their short maturities. The fair values of our marketable investments, 1.0 percent Convertible Senior Notes which matured in September 2016 (Convertible Notes) and contingent consideration are reported in Note 4—Investments and Note 5—Fair Value Measurements, respectively.
Fair Value Measurements	Fair Value Measurements Fair value is a market-based measurement, not an entity-specific measurement. The objective of a fair value measurement is to estimate the price to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date under current market conditions. Such transactions to sell an asset or transfer a liability are assumed to occur in the principal market for that asset or liability, or in the absence of the principal market, the most advantageous market for the asset or liability. Assets and liabilities subject to fair value measurement disclosures are required to be classified according to a three-level fair value hierarchy with respect to the inputs (or assumptions) used to determine fair value. The level in which an asset or liability is disclosed within the fair value hierarchy is based on the lowest level input that is significant to the related fair value measurement in its entirety. The guidance under the fair value measurement framework applies to other existing accounting guidance in the Financial Accounting Standards Board (FASB) codification that requires or permits fair value measurements. Refer to related disclosures in Note 5—Fair Value Measurements to these consolidated financial statements.
Cash Equivalents	Cash Equivalents Cash equivalents consist of highly liquid investments with maturities of three months or less from the date of acquisition and include money market funds, commercial paper, and certificates of deposit.
Marketable Investments	Marketable Investments Substantially all of our marketable investments are debt securities that we classify as held-to-maturity because of our positive intent and ability to hold the securities until maturity. Held-to-maturity securities are classified as either current or non-current assets on our consolidated balance sheets based on their contractual maturity dates and are recorded at amortized cost, adjusted for the amortization of discounts or premiums. Related discounts and premiums are amortized over the term of these securities as an adjustment to the yield using the effective interest method. We monitor our investment portfolio for impairment quarterly or more frequently if circumstances warrant. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, we record an impairment charge within earnings attributable to the estimated credit loss. In determining whether a decline in the value of an investment is other-than-temporary, we evaluate currently available factors that may include, among others: (1) general market conditions; (2) the duration and extent to which fair value has been less than the carrying value; (3) the investment issuer's financial condition and business outlook; and (4) our assessment as to whether it is more likely than not that we will be required to sell a security prior to recovery of its amortized cost basis.
Trade Receivables	Trade Receivables Trade receivables consist of short-term amounts due from customers and are stated at the amount we expect to collect. We establish an allowance for doubtful accounts, if any, based on our assessment of the collectability of specific customer accounts.
Inventories	Inventories Inventories are stated at the lower of cost (first-in, first-out method) or market (current replacement cost) and consist of the following, net of reserves (in millions): As of 2016 2015 Raw materials $ $ Work-in-progress Finished goods ​ ​ ​ ​ ​ ​ ​ ​ Total inventories $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The carrying amount of goodwill is not amortized but is subject to annual impairment testing. We conduct our impairment testing of goodwill annually during the fourth quarter, or more frequently, if impairment indicators exist. Initially, we evaluate various pertinent qualitative factors to assess whether it is more likely than not that the fair value of a reporting unit to which goodwill has been assigned is less than its carrying value. Such qualitative factors can include, among others: (1) industry and market conditions; (2) present and anticipated sales and cost factors; and (3) overall financial performance. If we conclude based on our qualitative assessment that it is more likely than not that the fair value of a reporting unit is less than its carrying value, we then measure the fair value of the reporting unit and compare its fair value to its carrying value (Step 1 of the goodwill impairment test). If the carrying amount of the reporting unit exceeds its fair value, then the amount of an impairment loss, if any, is measured as the excess of the recorded amount of goodwill over its implied fair value (Step 2 of the goodwill impairment test). We used a qualitative assessment for our goodwill impairment testing for 2016 and 2015. Our evaluation of goodwill completed during the years ended December 31, 2016 and 2015, resulted in no impairment losses. Indefinite-lived intangible assets are not amortized but are evaluated annually or more frequently for impairment if impairment indicators exist. Our indefinite-lived intangible assets include purchased in-process research and development projects, which were measured at their estimated fair values as of their acquisition dates. We used a qualitative assessment for our indefinite-lived intangible asset impairment testing. Our evaluation of indefinite-lived intangible assets completed during the years ended December 31, 2016 and 2015, resulted in no impairment losses. Intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an intangible asset may not be recoverable. Impairment losses are measured and recognized to the extent the carrying value of such assets exceeds their fair value. We recorded no impairment losses during the years ended December 31, 2016 and 2015. Goodwill and other intangible assets consists of the following (in millions): As of December 31, 2016 As of December 31, 2015 Gross Accumulated Net Gross Accumulated Net Goodwill $ $ — $ $ $ — $ Other intangible assets: Technology, patents and trade names ) ) In-process research and development — — Customer relationships and non-compete agreements ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ) $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Related amortization expense for the years ended December 31, 2016, 2015 and 2014, was $0.6 million, $1.1 million and $1.4 million, respectively. As of December 31, 2016, aggregate amortization expense relating to definite-lived intangible assets for each of the five succeeding years and thereafter is estimated at less than $1.0 million per year. In September 2015, we sold for $350.0 million in cash the Rare Pediatric Priority Review Voucher (PPRV) we received from the FDA in connection with the approval of Unituxin. The proceeds from the sale of the PPRV were recognized as a gain on the sale of an intangible asset as the PPRV did not have a carrying value on our consolidated balance sheet at the time of sale.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment is recorded at cost and depreciated over its estimated useful life using the straight-line method. The estimated useful lives of property, plant and equipment by major category are as follows: Land improvements 15 Years Buildings 25 - 39 Years Building improvements 10 - 39 Years Furniture, equipment and vehicles 3 - 25 Years Leasehold improvements Remaining lease term, or the estimated useful life of the improvement, whichever is shorter Property, plant and equipment consists of the following (in millions): As of December 31, 2016 2015 Land and land improvements $ $ Buildings, building improvements and leasehold improvements Buildings under construction Furniture, equipment and vehicles ​ ​ ​ ​ ​ ​ ​ ​ Less—accumulated depreciation ) ) ​ ​ ​ ​ ​ ​ ​ ​ Property, plant and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation expense for the years ended December 31, 2016, 2015 and 2014, was $31.0 million, $31.8 million and $30.8 million, respectively. Buildings under construction consists of direct costs relating to our construction projects.
Treasury Stock	Treasury Stock Repurchased treasury stock is recorded at cost, including commissions and fees. Treasury stock acquired in connection with the convertible note hedge on our Convertible Notes is recorded at the fair value on the acquisition date, which is the closing price of our common stock on that date. The cost of treasury shares sold or reissued is determined using the first-in, first-out method. Related gains and losses on sales of treasury stock are recognized as adjustments to stockholders' equity.
Revenue Recognition	Revenue Recognition Remodulin, Tyvaso, Orenitram and Unituxin We sell Remodulin, Tyvaso, Orenitram and Unituxin to distributors under similar contractual arrangements. We recognize sales of these products when title and risk of ownership pass to our distributors upon satisfactory delivery— i.e., when all of our performance obligations under our distribution agreements have been satisfied. We record sales of these products net of various product sales allowances in the period that associated revenues are recognized. These sales allowances include estimated rebates, prompt payment discounts and service fees paid to our distributors. Calculating these sales allowances involves the use of significant estimates and judgments and information obtained from external sources. We derive our provisions for estimated rebates from an analysis of historical levels of rebates to both state Medicaid agencies and commercial third-party payers by product, relative to sales of each product. In addition, for Orenitram patients, we determine our obligation for prescription drug discounts required by Medicare Part D for patients within the coverage gap based on estimations of the number of patients and the period that such patients will remain within the coverage gap. In formulating our estimates, we also consider the impact of anticipated changes in our product pricing, if any, sales trends and government rebate programs, particularly as they relate to eligibility requirements and/or rebate pricing. Prompt pay discounts are estimated based on our experience with sales to eligible distributors. Our distributors have routinely taken advantage of these discounts and we expect them to continue to do so. We pay our distributors for contractual services rendered and accrue for related fees based on contractual rates applied to the estimated units of service provided by distributors for a given financial reporting period. Our distributors do not possess return rights for Remodulin, Tyvaso and Orenitram; however, the sales terms for Unituxin include return rights that extend throughout the distribution channel. The financial impact of return rights for Unituxin is not material. We also provide exchange rights for all products in the event that a product is damaged during shipment or expires. Exchanges for damaged product are highly infrequent and the impact of expired product is not material. We do not record a reserve for estimated exchange rights for any of these products in the period of sale. Adcirca Adcirca is manufactured for us by Eli Lilly and Company (Lilly) and distributed through Lilly's pharmaceutical wholesaler network. Specifically, Lilly handles all of the administrative functions associated with the sale of Adcirca on our behalf, including the receipt and processing of customer purchase orders, shipment to customers, and invoicing and collection of customer payments. In addition, the sales terms for Adcirca include return rights that extend throughout the distribution channel. We recognize sales of Adcirca on a gross basis (net of allowances) upon delivery to customers due to the following factors: (1) we are responsible for the acceptability of the product purchased by wholesalers; (2) we bear all inventory risk, as title and risk of loss pass to us at the shipping point from Lilly's manufacturing facility; (3) we assume credit risk if Lilly is unable to collect amounts due from customers; and (4) we assume the risk and cost of a product recall, if required. We recognize sales of Adcirca net of: (1) estimated rebates under government drug discount programs and commercial third-party payer contracts; (2) prompt pay discounts; (3) allowances for product returns; and (4) wholesaler fees. We estimate our liability for rebates based on an analysis of historical levels of rebates to both Medicaid and commercial third-party payers and we consider the impact of sales trends, changes in government and commercial rebate programs and anticipated changes in Adcirca's pricing. Prompt pay discounts are estimated based on our experience with sales to eligible distributors. We derive our allowance for returns based on historical return rates accumulated since the commercial launch of Adcirca in 2009. Wholesaler fees are based on contractual percentages of sales to wholesalers.
Research and Development	Research and Development Research and development costs are expensed as incurred except for refundable payments made in advance of services to be provided to us. Related expenses consist of internal labor and overhead, costs to acquire pharmaceutical products and product rights for development, materials used in clinical trials and amounts paid to third parties for services and materials relating to drug development and clinical trials. We recognize the following as research and development expense in the period related costs are incurred: • costs associated with in-house or contracted manufacturing activities prior to receiving FDA approval for such facilities, or for major unproven changes to our manufacturing processes; • costs incurred in licensing the rights to technologies in the research and development stage that have no alternative future use; and • up-front payments made in connection with arrangements to obtain license and distribution rights to pharmaceutical product candidates prior to regulatory approval, absent any alternative future use.
Share-Based Compensation	Share-Based Compensation Our share tracking awards plans require cash settlement upon exercise and are classified as a liability. Accordingly, the fair value of related cash-settled awards is re-measured at each reporting date until awards are exercised or are otherwise no longer outstanding. Related changes in the fair value of outstanding cash-settled awards at each financial reporting date are recognized as adjustments to share-based compensation expense. Generally, the fair value of a stock option grant is measured on its grant date and related compensation expense is recognized ratably over the requisite service period. We issue new shares of our common stock upon the exercise of stock options. We measure the fair value of restricted stock units using the stock price on the date of grant and related compensation expense is recognized ratably over the vesting period. Each restricted stock unit entitles the holder to receive one share of our common stock upon vesting. We issue new shares of our common stock upon the vesting of restricted stock units. We measure the fair value of stock to be purchased through our employee stock purchase plan at the beginning of an offering period, or grant date, and recognize related compensation expense ratably over the requisite service period (the offering period). We issue new shares of our common stock upon the end of each offering period, or exercise date.
Income Taxes	Income Taxes Income taxes are accounted for in accordance with the asset and liability method. Accordingly, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their tax bases. Deferred tax assets and liabilities are measured using the enacted tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance when, in our judgment, it is more likely than not that some or all of the deferred tax assets will not be realized. Financial statement recognition of a tax position taken or expected to be taken in a tax return is determined based on a more likely than not threshold of that position being sustained. If the tax position meets this threshold, the benefit to be recognized is measured as the largest amount that is more likely than not to be realized upon ultimate settlement. It is our policy to record interest and penalties related to uncertain tax positions as a component of income tax expense.
Earnings (Loss) per Share	Earnings (Loss) per Share Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period, plus the potential dilutive effect of other securities if such securities were converted or exercised. During periods in which we incur net losses, both basic and diluted loss per share is calculated by dividing the net loss by the weighted average shares outstanding—potentially dilutive securities are excluded from the calculation because their effect would be anti-dilutive.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that are exposed to credit risk consist of cash, money market funds, commercial paper, marketable investments, and trade receivables. We maintain our cash and money market funds with financial institutions that are federally insured. While balances deposited in these institutions often exceed Federal Deposit Insurance Corporation limits, we have not experienced any losses on related accounts to date. Furthermore, we limit our risk exposure by maintaining funds in financial institutions that we believe are creditworthy and financially sound. Our investments in marketable debt securities have been issued by corporate entities and federally-sponsored enterprises with high credit ratings. We mitigate investment risks by investing in highly-rated securities with relatively short maturities that we believe do not subject us to undue investment or credit risk. In addition, our investment policy does not provide for investments in complex or structured financial instruments. At any given time, our trade receivables are concentrated among a small number of principal customers. If any of these financial institutions, issuers or customers fail to perform their obligations under the terms of these financial instruments, our maximum exposure to potential losses would be equal to amounts reported on our consolidated balance sheets.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Schedule of inventories, net of reserves	Inventories are stated at the lower of cost (first-in, first-out method) or market (current replacement cost) and consist of the following, net of reserves (in millions): As of 2016 2015 Raw materials $ $ Work-in-progress Finished goods ​ ​ ​ ​ ​ ​ ​ ​ Total inventories $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of goodwill and other intangible assets	Goodwill and other intangible assets consists of the following (in millions): As of December 31, 2016 As of December 31, 2015 Gross Accumulated Net Gross Accumulated Net Goodwill $ $ — $ $ $ — $ Other intangible assets: Technology, patents and trade names ) ) In-process research and development — — Customer relationships and non-compete agreements ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ) $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of property, plant and equipment and the estimated useful lives	Land improvements 15 Years Buildings 25 - 39 Years Building improvements 10 - 39 Years Furniture, equipment and vehicles 3 - 25 Years Leasehold improvements Remaining lease term, or the estimated useful life of the improvement, whichever is shorter Property, plant and equipment consists of the following (in millions): As of December 31, 2016 2015 Land and land improvements $ $ Buildings, building improvements and leasehold improvements Buildings under construction Furniture, equipment and vehicles ​ ​ ​ ​ ​ ​ ​ ​ Less—accumulated depreciation ) ) ​ ​ ​ ​ ​ ​ ​ ​ Property, plant and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Investments
Schedule of marketable investments classified as held-to-maturity	Marketable investments classified as held-to-maturity consist of the following (in millions): As of December 31, 2016 Amortized Gross Gross Fair Government-sponsored enterprises $ $ — $ — $ Corporate notes and bonds — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported under the following captions on the consolidated balance sheet: Current marketable investments $ Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2015 Amortized Gross Gross Fair Government-sponsored enterprises $ $ — $ ) $ Corporate notes and bonds — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported under the following captions on the consolidated balance sheet: Current marketable investments $ Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position	The following table summarizes gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position (in millions) As of December 31, 2016 2015 Fair Gross Fair Gross Government-sponsored enterprises: Continuous unrealized loss position less than one year $ — $ — $ $ ) Continuous unrealized loss position greater than one year — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — — ) Corporate notes and bonds: Continuous unrealized loss position less than one year — — — Continuous unrealized loss position greater than one year — — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ — $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of the contractual maturities of held-to-maturity marketable investments	The following table summarizes the contractual maturities of held-to-maturity marketable investments (in millions): As of Amortized Fair Due in less than one year $ $ Due in one to two years Due in three to five years — — Due after five years — — ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Schedule of assets and liabilities subject to fair value measurements	Assets and liabilities subject to fair value measurements are as follows (in millions): As of December 31, 2016 Level 1 Level 2 Level 3 Balance Assets Money market funds (1) $ $ — $ — $ Federally-sponsored and corporate debt securities (2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities Contingent consideration (4) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ — $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2015 Level 1 Level 2 Level 3 Balance Assets Money market funds (1) $ $ — $ — $ Federally-sponsored and corporate debt securities (2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities Convertible notes due 2016 (3) $ $ — $ — $ Contingent consideration (4) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total liabilities $ $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Included in cash and cash equivalents on the accompanying consolidated balance sheets. (2) Included in current and non-current marketable investments on the accompanying consolidated balance sheets. The fair value of these securities is principally measured or corroborated by trade data for identical securities in which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded. See also Note 4—Investments—Marketable Investments—Held-to-Maturity Investments to these consolidated financial statements. (3) Included in other current liabilities on the accompanying consolidated balance sheets. The Convertible Notes matured on September 15, 2016. The carrying value of the Convertible Notes as of December 31, 2015 was $5.4 million. The fair value of our Convertible Notes was estimated using Level 1 observable inputs since our Convertible Notes were trading with sufficient frequency such that we believed related pricing could be used as the primary basis for measuring their fair value. As of December 31, 2015, the fair value of the Convertible Notes was substantially higher than their book value. This was primarily due to the excess conversion value of the Convertible Notes compared to the Convertible Notes' par value, and the fact that any such excess would be paid in shares of our common stock. (4) Included in other non-current liabilities on the accompanying consolidated balance sheets. The fair value of contingent consideration has been estimated using probability weighted discounted cash flow models (DCF). The DCF incorporates Level 3 inputs including estimated discount rates that we believe market participants would consider relevant in pricing and the projected timing and amount of cash flows, which are estimated and developed, in part, based on the requirements specific to each acquisition agreement. We analyze and evaluate these fair value measurements quarterly to determine whether valuation inputs continue to be relevant and appropriate or whether current period developments warrant adjustments to valuation inputs and related measurements.

Accounts Payable and Accrued 32

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Accounts Payable and Accrued Expenses
Schedule of accounts payable and accrued expenses	Accounts payable and accrued expenses consist of the following by major categories (in millions): As of 2016 2015 Accounts payable $ $ Accrued expenses: Sales related (royalties, rebates and fees) $ $ Payroll related Other ​ ​ ​ ​ ​ ​ ​ ​ Total accrued expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ Total accounts payable and accrued expenses $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Share Tracking Awards Plans (Ta

Share Tracking Awards Plans (Tables) - Share tracking award plans (STAP)	12 Months Ended
	Dec. 31, 2016
Awards granted under the STAP
Schedule of assumptions to estimate the fair value of outstanding STAP awards	As of December 31, 2016 2015 2014 Expected volatility % % % Risk-free interest rate % % % Expected term of awards (in years) Expected forfeiture rate % % % Expected dividend yield % % %
Summary of the status and activity of the STAP awards	Number of Weighted- Weighted Aggregate Outstanding at January 1, 2016 $ Granted — — Exercised ) Forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of share-based compensation (benefit) expense recognized in connection with the STAP	Share-based compensation (benefit) expense recognized in connection with the STAP is as follows (in millions): Year Ended December 31, 2016 2015 2014 Cost of product sales $ — $ $ Research and development ) Selling, general and administrative ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation (benefit) expense before tax ) Related income tax expense (benefit) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation (benefit) expense, net of tax $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation capitalized as part of inventory $ — $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt
Schedule of components of interest expense presented on the entity's consolidated statements of operations	Details of interest expense presented on our consolidated statements of operations are as follows (in millions): Year Ended 2016 2015 2014 Contractual coupon rate of interest—convertible notes $ — $ $ Discount amortization—convertible notes ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest expense—convertible notes Other interest expense (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total interest expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Represents interest expense related to debt and amortization of issuance costs.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Schedule of future minimum lease payments under non-cancelable operating leases	Future minimum lease payments under non-cancelable operating leases as of December 31, 2016, are as follows (in millions): Year Ending December 31, 2017 $ 2018 2019 2020 ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of future milestone payments under assignment and license agreements	Future milestone payments based on our estimates of the timing and probability of achieving milestones specified under these arrangements are as follows (in millions): Year Ending December 31, (1) 2017 $ 2018 2019 2020 2021 Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) The amounts and timing of future milestone payments may vary depending on when related milestones will be attained, if at all.

Temporary Equity (Tables)

Temporary Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Temporary Equity
Schedule of components of temporary equity	Components comprising the carrying value of temporary equity include the following (in millions): As of 2016 2015 Reclassification of Equity Component (1) $ — $ Common stock subject to repurchase (2) ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Represents the reclassification of the Equity Component equal to the unamortized debt discount of our Convertible Notes as of December 31, 2015 from additional paid-in capital to temporary equity. Our Convertible Notes were convertible at the election of the holders as noted in Note 8— Debt — Convertible Notes Due 2016 . The Convertible Notes matured in September 2016. (2) In connection with our license agreement with Toray Industries Inc. (Toray), we issued 200,000 shares of our common stock (which have since split into 400,000 shares) to Toray in 2007, and provided Toray the right to require us to repurchase the shares at a price of $27.21 per share.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Common Share
Schedule of components of basic and diluted earnings per share	The components of basic and diluted earnings per share comprised the following (in millions, except per share amounts): Year Ended December 31, 2016 2015 2014 Numerator: Net income $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted average outstanding shares—basic Effect of dilutive securities (1) : Convertible notes — Warrants Stock options, restricted stock units and employee stock purchase plan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average shares—diluted (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per common share: Basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options and warrants excluded from calculation (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Calculated using the treasury stock method. (2) Certain convertible notes, stock options and warrants have been excluded from the computation of diluted earnings per share because their impact would be anti-dilutive. Under our convertible note hedge agreement, we were entitled to receive shares required to be issued to investors upon conversion of our Convertible Notes. Since related shares used to compute dilutive earnings per share would be anti-dilutive, they have been excluded from the calculation above.
Stock Options
Stock Option Plan
Summary of weighted-average assumptions to estimate the grant date fair value of stock option	Year Ended 2016 2015 2014 Expected volatility % % % Risk-free interest rate % % % Expected term of options (in years) Expected forfeiture rate (1) % % % Expected dividend yield % % % (1) During 2016 we issued stock options to all employees, which resulted in an increase in the forfeiture rate compared to prior years.
Schedule of stock options activity	Options Weighted- Weighted Aggregate Outstanding at January 1, 2016 $ Granted Exercised ) Forfeited ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest at December 31, 2016 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of total share-based compensation expense relating to stock options	Total share-based compensation expense relating to stock options is as follows (in millions): Year Ended December 31, 2016 2015 2014 Cost of product sales $ $ — $ — Research and development — — Selling, general and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense before tax Related income tax benefit ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense, net of tax $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of stock option exercise data	Stock option exercise data is summarized below (dollars in millions): Year Ended December 31, 2016 2015 2014 Number of options exercised Cash received from options exercised $ $ $ Total intrinsic value of options exercised $ $ $ Tax benefits realized from options exercised $ $ $

Accumulated Other Comprehensi38

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2016
Accumulated Other Comprehensive Loss
Schedule of changes in accumulated other comprehensive loss by component, net of tax	The following table includes changes in accumulated other comprehensive loss by component, net of tax (in millions): Defined Benefit (1) Foreign Currency (2) Total Balance, January 1, 2016 $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) Amounts reclassified from accumulated other comprehensive loss — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive income (loss) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, December 31, 2016 $ $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Defined Benefit (1) Foreign Currency Total Balance, January 1, 2015 $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) ) Amounts reclassified from accumulated other comprehensive loss — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net current-period other comprehensive income (loss) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, December 31, 2015 $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Refer to Note 14— Employee Benefit Plans — Supplemental Executive Retirement Plan , which identifies the captions within our consolidated statement of operations where reclassification adjustments were recognized and their associated tax impact. (2) In the fourth quarter of 2016, we changed the functional currency for our foreign entities to the U.S. dollar. The loss on foreign currency translation attributable to each foreign entity at the time of this change will remain in accumulated other comprehensive loss until the sale or substantial liquidation of the foreign entity.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Taxes
Schedule of components of income tax expense (benefit)	Components of income tax expense (benefit) consist of the following (in millions): Year Ended December 31, 2016 2015 2014 Current: Federal $ $ $ State ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total current Deferred Federal ) ) State ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total deferred ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of income tax expense computed at the statutory federal tax rate to income tax expense	Presented below is a reconciliation of income tax expense computed at the statutory federal tax rate to income tax expense as reported (in millions): Year Ended December 31, 2016 2015 2014 Federal taxes at 35% $ $ $ State taxes, net of federal benefit General business credits ) ) ) Section 199 deduction ) ) ) Nondeductible compensation expense ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of net deferred tax assets	Components of the net deferred tax assets are as follows (in millions): As of 2016 2015 Deferred tax assets: Intangible assets $ $ Nonqualified stock options SERP STAP awards Other ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets Deferred tax liabilities: Plant and equipment principally due to differences in depreciation ) ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets before valuation allowance Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of beginning and ending balances of unrecognized tax benefits	A reconciliation of the beginning and ending balances of unrecognized tax benefits is as follows (in millions): As of 2016 2015 Unrecognized tax benefits at the beginning of year $ $ Lapse of statute of limitations — ) ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized tax benefits at the end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Employee Benefit Plans
Schedule of reconciliation of the beginning and ending balances of the projected benefit obligation	A reconciliation of the beginning and ending balances of the projected benefit obligation is presented below (in millions): Year Ended 2016 2015 Projected benefit obligation at the beginning of the year $ $ Service cost Interest cost Plan amendments — Benefits paid — ) Actuarial gain (1) ) ) ​ ​ ​ ​ ​ ​ ​ ​ Projected benefit obligation at the end of the year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets at the end of the year — — ​ ​ ​ ​ ​ ​ ​ ​ Unfunded at end of the year $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount included in Other current liabilities (2) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) During the second quarter of 2016, certain participants in the SERP departed before retirement age under the terms of the SERP. As a result, we remeasured the benefit obligation under the SERP as of June 30, 2016, and recorded a reduction to the benefit obligation with a corresponding increase to "Actuarial gain arising during period, net of tax" within "Accumulated other comprehensive loss" of $7.1 million. As part of the re-measurement of the benefit obligation, we updated the discount rate we used to measure our SERP obligation to 3.36 percent. The discount rate as of December 31, 2015 was 3.82 percent. (2) The amount included under the caption "Other current liabilities" on our consolidated balance sheet represents the benefit obligation due to participants who are eligible to retire.
Schedule of future estimated benefit payments, based on current assumptions, including election of lump-sum distributions and expected future service	Future estimated benefit payments, based on current assumptions, including election of lump-sum distributions and expected future service, are as follows (in millions): Year Ended December 31, 2017 $ 2018 — 2019 2020 — 2021 — Thereafter ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of weighted-average assumptions used to measure the SERP obligation	Year Ended 2016 2015 Discount Rate % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salary Increases % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of net periodic pension cost recognized	The components of net periodic pension cost recognized on our consolidated statements of operations consist of the following (in millions): Year Ended 2016 2015 2014 Service cost $ $ $ Interest cost Amortization of prior service cost Amortization of net actuarial (gain) loss ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components reclassified from accumulated other comprehensive loss	Reclassification adjustments related to the SERP from accumulated other comprehensive loss to the statements of operations by line item and the tax impact of these reclassifications is presented below (in millions): Components Reclassified from Accumulated Other Comprehensive Loss (1) As of As of Prior service cost: Research and development $ $ Selling, general and administrative ​ ​ ​ ​ ​ ​ ​ ​ Total Amortization of net actuarial (gain) loss: Research and development ) — Selling, general and administrative ) ​ ​ ​ ​ ​ ​ ​ ​ Total ) Total prior service cost and amortization of net actuarial (gain) loss Tax benefit ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Refer to Note 12— Accumulated Other Comprehensive Loss .
Schedule of amounts recognized in other comprehensive income (loss)	Amounts relating to the SERP that have been recognized in other comprehensive income (loss) are as follows (in millions): Year Ended 2016 2015 2014 Net unrecognized actuarial gain $ $ $ Net unrecognized prior service (benefit) cost ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Tax benefit ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of amounts included in accumulated other comprehensive loss that have not yet been recognized as a component of net periodic pension cost	The table below presents amounts relating to the SERP included in accumulated other comprehensive loss that have not yet been recognized as a component of net periodic pension cost on our consolidated statements of operations (in millions): Year Ended 2016 2015 2014 Net unrecognized actuarial (gain) loss $ ) $ $ Net unrecognized prior service cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ) Tax expense (benefit) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total, net of tax $ ) $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of estimated amounts included in accumulated other comprehensive loss that are expected to be recognized as components of net periodic pension expense	Estimated amounts included in accumulated other comprehensive loss as of December 31, 2016, that are expected to be recognized as components of net periodic pension cost on our statements of operations for the year ended December 31, 2017, comprise the following (in millions): Amortization of prior service cost $ Amortization of net actuarial gain ) ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Information
Schedule of net product sales, cost of product sales and gross profit for each commercial product	Net product sales, cost of product sales and gross profit for each of our commercial products were as follows (in millions): Remodulin Tyvaso Adcirca Orenitram Unituxin Total Year Ended December 31, 2016 Net product sales $ $ $ $ $ $ Cost of product sales ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2015 (1) Net product sales $ $ $ $ $ $ Cost of product sales ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2014 (2) Net product sales $ $ $ $ $ — $ Cost of product sales — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit $ $ $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) We commenced sales of Unituxin during the third quarter of 2015. (2) We commenced sales of Orenitram during the second quarter of 2014.
Schedule of net revenues from external customers by geographic area	Total revenues from external customers by geographic area are as follows (in millions): Year Ended December 31, 2016 2015 2014 United States $ $ $ Rest-of-World (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (2) $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Primarily Europe. (2) Total includes other revenue of $5.2 million and $9.0 million for the years ended December 31, 2015 and 2014, respectively.
Schedule of long-lived assets (property, plant and equipment) located by geographic area	Long-lived assets (property, plant and equipment) located by geographic area are as follows (in millions): Year Ended December 31, 2016 2015 2014 United States $ $ $ Rest-of-World ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Quarterly Financial Informati42

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information (Unaudited)
Summary of quarterly financial information	Summarized quarterly financial information for each of the years ended December 31, 2016 and 2015 are as follows (in millions, except per share amounts): Quarter Ended December 31, September 30, June 30, March 31, Total revenues $ $ $ $ Cost of product sales Gross profit Net income (1) Net income per share—basic $ $ $ $ Net income per share—diluted $ $ $ $ Quarter Ended December 31, September 30, June 30, March 31, Total revenues $ $ $ $ Cost of product sales Gross profit Net income (loss) (2)(3) ) Net income (loss) per share—basic $ $ $ $ ) Net income (loss) per share—diluted $ $ $ $ ) (1) Operating results for the quarter ended December 31, 2016, September 30, 2016, June 30, 2016 and March 31, 2016 include $64.2 million, $28.7 million, $(7.0) million and $(95.5) million net of tax expense (benefit) to operating expenses for STAP related share-based compensation expense, respectively. (2) Operating results for the quarter ended December 31, 2015, September 30, 2015, June 30, 2015 and March 31, 2015 include $73.9 million, $(75.7) million, $27.5 million and $145.0 million net of tax expense (benefit) to operating expenses for STAP related share-based compensation expense, respectively. (3) Operating results for the quarter ended September 30, 2015, include a gain on sale of the PPRV we received from the FDA in connection with the approval of Unituxin, for $350.0 million in cash. The proceeds from the sale of the PPRV were recognized as a gain on the sale of an intangible asset, as the PPRV did not have a carrying value on our consolidated balance sheet at the time of sale.

Litigation (Tables)

Litigation (Tables)	12 Months Ended
	Dec. 31, 2016
Litigation
Schedule of patent expiration dates	U.S. Patent No. Expiration Date 8,252,839 May 2024 9,050,311 May 2024 7,544,713 July 2024 7,417,070 July 2026 8,497,393 December 2028 8,747,897 October 2029 8,410,169 February 2030 8,349,892 January 2031

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Fair Value of Financial Instruments (Details)	Dec. 31, 2016	Oct. 31, 2011
Convertible Notes Due 2016
Fair Value of Financial Instruments
Stated percentage rate	1.00%	1.00%

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Inventories
Raw materials	$ 25.4	$ 23.1
Work-in-progress	24.9	22.5
Finished goods	49.7	35.7
Total inventories	$ 100	$ 81.3

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and other intangible assets
Goodwill, Gross			$ 10.3	$ 10.3
Goodwill, Net			10.3	10.3
Total Goodwill and other intangible assets, Gross			42.6	36.6
Other intangible assets, Accumulated Amortization			(8.8)	(8.2)
Total Goodwill and other intangible assets, Net			33.8	28.4
Amortization expense relating to intangible assets			0.6	1.1	$ 1.4
Impairment loss for Goodwill			0	0
Impairment losses of indefinite-lived intangible assets			0	0
Impairment losses of finite-lived intangible assets			0	0
Amortization relating to other intangible assets
Proceeds from sale of intangible asset		$ 350		350
Maximum
Amortization relating to other intangible assets
2,017			1
2,018			1
2,019			1
2,020			1
2,021			1
Thereafter			1
Technology, patents and trade names
Goodwill and other intangible assets
Other intangible assets, Gross			6.5	6.5
Other intangible assets, Accumulated Amortization			(4.8)	(4.7)
Other intangible assets, Net			1.7	1.8
In-process research and development
Goodwill and other intangible assets
Other intangible assets, Gross			21.5	15.5
Other intangible assets, Net			21.5	15.5
Customer relationships and non-compete agreements
Goodwill and other intangible assets
Other intangible assets, Gross			4.3	4.3
Other intangible assets, Accumulated Amortization			(4)	(3.5)
Other intangible assets, Net			$ 0.3	$ 0.8
PPRV Licensing Agreement
Amortization relating to other intangible assets
Proceeds from sale of intangible asset	$ 350

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment
Property, plant and equipment, gross	$ 664.3	$ 650.7
Less-accumulated depreciation	(175)	(154.9)
Property, plant and equipment, net	489.3	495.8	$ 478.4
Depreciation expense	$ 31	31.8	$ 30.8
Land improvements
Property, Plant and Equipment
Estimated useful life	15 years
Land and land improvements
Property, Plant and Equipment
Property, plant and equipment, gross	$ 60.1	61.1
Buildings, building improvements and leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	$ 409.9	418.2
Buildings | Minimum
Property, Plant and Equipment
Estimated useful life	25 years
Buildings | Maximum
Property, Plant and Equipment
Estimated useful life	39 years
Building improvements | Minimum
Property, Plant and Equipment
Estimated useful life	10 years
Building improvements | Maximum
Property, Plant and Equipment
Estimated useful life	39 years
Buildings under construction
Property, Plant and Equipment
Property, plant and equipment, gross	$ 44.6	26.5
Furniture, equipment and vehicles
Property, Plant and Equipment
Property, plant and equipment, gross	$ 149.7	$ 144.9
Furniture, equipment and vehicles | Minimum
Property, Plant and Equipment
Estimated useful life	3 years
Furniture, equipment and vehicles | Maximum
Property, Plant and Equipment
Estimated useful life	25 years

Summary of Significant Accoun48

Summary of Significant Accounting Policies - Share-Based Compensation and Income Taxes (Details)	Dec. 31, 2016item
Restricted stock units
Share-Based Compensation
Number of shares of common stock entitled for each unit upon vesting	1

Investments - Held-to-Maturity

Investments - Held-to-Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Marketable investments classified as held-to-maturity:
Amortized Cost	$ 30.1	$ 160
Gross Unrealized Losses		(0.2)
Fair Value	30.1	159.8
Government-sponsored enterprises
Marketable investments classified as held-to-maturity:
Amortized Cost	19.3	53.3
Gross Unrealized Losses		(0.2)
Fair Value	19.3	53.1
Corporate notes and bonds
Marketable investments classified as held-to-maturity:
Amortized Cost	10.8	106.7
Fair Value	$ 10.8	$ 106.7

Investments - Current and Noncu

Investments - Current and Noncurrent (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$ 27.8	$ 122
Non-current marketable investments	2.3	38
Total marketable investments	$ 30.1	$ 160

Investments - Gross Unrealized

Investments - Gross Unrealized Losses (Details) $ in Millions	Dec. 31, 2015USD ($)
Continuous unrealized loss position, Fair Value
Fair Value, Total	$ 111.9
Continuous unrealized loss position, Gross Unrealized Loss
Gross Unrealized Loss, Total	(0.2)
Government-sponsored enterprises
Continuous unrealized loss position, Fair Value
Less than one year, Fair value	48.1
Fair Value, Total	48.1
Continuous unrealized loss position, Gross Unrealized Loss
Less than one year, Gross Unrealized Loss	(0.2)
Gross Unrealized Loss, Total	(0.2)
Corporate notes and bonds
Continuous unrealized loss position, Fair Value
Less than one year, Fair value	63.8
Fair Value, Total	$ 63.8

Investments - Contractual Matur

Investments - Contractual Maturities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost
Due in less than one year, Amortized Cost	$ 27.8
Due in one to two years, Amortized Cost	2.3
Total marketable investments	30.1	$ 160
Fair Value
Due in less than one year, Fair Value	27.8
Due in one to two years, Fair Value	2.3
Fair Value	$ 30.1	$ 159.8

Investments - Held at Cost (Det

Investments - Held at Cost (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2015	May 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cost Method Investments
Payments to acquire investments			$ 36	$ 54.2	$ 45
Privately-held Companies
Cost Method Investments
Investments held at cost			173.2
Synthetic Genomics Inc
Cost Method Investments
Investments held at cost			$ 100
Payments to acquire investments	$ 50	$ 50

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Federally-sponsored and corporate debt securities	$ 30.1	$ 159.8
Convertible Notes Due 2016
Liabilities
Carrying amount		5.4
Recurring fair value measurements | Balance
Assets
Money market funds	534.4	496.4
Federally-sponsored and corporate debt securities	30.1	159.8
Total assets	564.5	656.2
Liabilities
Convertible notes due 2016		16
Contingent consideration	10.4	9.4
Total liabilities	10.4	25.4
Recurring fair value measurements | Level 1
Assets
Money market funds	534.4	496.4
Total assets	534.4	496.4
Liabilities
Convertible notes due 2016		16
Total liabilities		16
Recurring fair value measurements | Level 2
Assets
Federally-sponsored and corporate debt securities	30.1	159.8
Total assets	30.1	159.8
Recurring fair value measurements | Level 3
Liabilities
Contingent consideration	10.4	9.4
Total liabilities	$ 10.4	$ 9.4

Accounts Payable and Accrued 55

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts payable
Accounts payable	$ 8.1	$ 7.5
Accrued expenses:
Sales related (royalties, rebates and fees)	55.7	52.8
Payroll related	30.6	31.4
Other	9.8	11.7
Total accrued expenses	96.1	95.9
Total accounts payable and accrued expenses	$ 104.2	$ 103.4

Share Tracking Awards Plans - G

Share Tracking Awards Plans - General (Details) - Share tracking award plans (STAP) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Awards granted under the STAP
Grant expiration period from the grant date	10 years
Share-based awards, vesting period	4 years
Aggregate STAP liability	$ 268.9	$ 354.7
Long term portion of STAP liability	$ 74.1	$ 80.2
Expected volatility maximum period	5 years
Weighted-average assumptions used to measure the fair value of the outstanding STAP awards:
Expected volatility (as a percent)	36.10%	35.30%	34.00%
Risk-free interest rate (as a percent)	1.40%	1.40%	1.30%
Expected term of awards (in years)	2 years 6 months	3 years 4 months 24 days	4 years
Expected forfeiture rate (as a percent)	8.80%	8.80%	9.30%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Closing price of common stock (in dollars per share)	$ 143.43	$ 156.61	$ 129.49
Share-based awards activity
Outstanding at the beginning of the year (in shares)	6,845,163
Exercised (in shares)	(1,139,612)
Forfeited (in shares)	(591,713)
Outstanding at the end of the year (in shares)	5,113,838	6,845,163
Exercisable at the end of the year (in shares)	2,564,858
Expected to vest at the end of the year (in shares)	2,315,483
Share awards, Weighted-Average Exercise Price
Outstanding at the beginning of the year (in dollars per share)	$ 86.86
Exercised (in dollars per share)	61.08
Forfeited (in dollars per share)	96.32
Outstanding at the end of the year (in dollars per share)	91.51	$ 86.86
Exercisable at the end of the year (in dollars per share)	88.46
Expected to vest at the end of the year (in dollars per share)	$ 93.41
Share awards, Weighted Average Remaining Contractual Term (Years)
Outstanding at the end of the year	6 years 6 months
Exercisable at the end of the year	6 years 1 month 6 days
Expected to vest at the end of the year	6 years 10 months 24 days
Share awards, Aggregate Intrinsic Value
Outstanding at the end of the year (in dollars)	$ 290.3
Exercisable at the end of the year (in dollars)	151.3
Expected to vest at the end of the year (in dollars)	$ 128.6
Awards granted during the period, weighted average grant date fair value (in dollars per share)		$ 58.52	$ 33.82

Share Tracking Awards Plans - E

Share Tracking Awards Plans - Expense Recognized (Details) - Share tracking award plans (STAP) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share based compensation expense recognized in connection with the STAP
Share-based compensation (benefit) expense before tax									$ (15.2)	$ 274.2	$ 159.5
Related income tax expense (benefit)									5.6	(103.5)	(56.6)
Share-based compensation (benefit) expense, net of tax	$ 64.2	$ 28.7	$ (7)	$ (95.5)	$ 73.9	$ (75.7)	$ 27.5	$ 145	(9.6)	170.7	102.9
Share-based compensation capitalized as part of inventory										7.1	2
Cash payments on awards exercised during the period									69.5	248.8	144.1
Cost of product sales
Share based compensation expense recognized in connection with the STAP
Share-based compensation (benefit) expense before tax										8.7	4.3
Research and development
Share based compensation expense recognized in connection with the STAP
Share-based compensation (benefit) expense before tax									(11.8)	87.4	72.3
Selling, general and administrative
Share based compensation expense recognized in connection with the STAP
Share-based compensation (benefit) expense before tax									$ (3.4)	$ 178.1	$ 82.9

Debt - General (Details)

Debt - General (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2016	Oct. 31, 2011
Credit Agreement 2016
Debt
Maximum borrowing capacity		$ 1,000
Period of extension in maturity		1 year
Revolving credit facility
Debt
Maximum borrowing capacity	$ 75
Debt, maturity term	1 year
Convertible Notes Due 2016
Debt
Debt aggregate principal value			$ 250
Convertible Senior Notes, stated percentage		1.00%	1.00%
Conversion price (in dollars per share)			$ 47.69
Convertible debt, number of shares into which convertible			5.2
Carrying value of convertible notes
Value of convertible note settled due to conversion requests		$ 5.6
Shares issued for conversion of convertible notes (in shares)		0.1
Number of common shares bought under note hedge		0.1

Debt - Convertible Note Hedge a

Debt - Convertible Note Hedge and Warrant Transactions (Details) - Convertible Notes Due 2016 - $ / shares	2 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016
Sale of warrant
Share warrant, number of shares		5,200,000
Share warrant, strike price (in dollars per share)		$ 67.56
Shares issued upon expiration of warrants (shares)	2,800,000	1,100,000
Purchased call options
Purchase of call options
Convertible note hedge, approximate number of shares that can be purchased		5,200,000
Convertible note hedge, exercise price (in dollars per share)		$ 47.69

Debt - Interest Expense (Detail

Debt - Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest expense
Other interest expense	$ 3.8	$ 1.3	$ 4.4
Total interest expense	3.9	4.7	17.6
Convertible Notes Due 2016
Interest expense
Contractual coupon rate of interest - convertible notes		0.4	2.1
Discount amortization - convertible notes	0.1	3	11.1
Interest expense - convertible notes	$ 0.1	$ 3.4	$ 13.2

Commitments and Contingencies61

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Future minimum lease payments under non-cancelable operating leases
2,017	$ 3.8
2,018	2.8
2,019	0.4
2,020	0.2
Total	7.2
Total rent expense	4.4	$ 3.8	$ 3.6
Future milestone payments under Assignment and License Agreements
2,017	9.8
2,018	1.6
2,019	2.3
2,020	1.5
2,021	0.7
Thereafter	5.9
Total	$ 21.8

Temporary Equity (Details)

Temporary Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Temporary equity
Total	$ 10.9	$ 11.1
Temporary equity component in convertible note due 2016
Temporary equity
Reclassification of Equity Component		0.2
Temporary equity common stocks subject to repurchase
Temporary equity
Common stock subject to repurchase	$ 10.9	$ 10.9
Common stock issued (in shares)	200,000
Common stock issued split (in shares)	400,000
Repurchase price (in dollars per share)	$ 27.21

Stockholders' Equity - Earnings

Stockholders' Equity - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 110.3	$ 161.8	$ 206.1	$ 235.5	$ 104.6	$ 464.4	$ 99.2	$ (16.6)	$ 713.7	$ 651.6	$ 340.1
Denominator:
Weighted average outstanding shares - basic									43.8	46	48.2
Effect of dilutive securities:
Convertible notes (in shares)										0.9	2.6
Warrants (in shares)									2.3	3	1.9
Stock options, restricted stock units and employee stock purchase plan (in shares)									0.7	1.3	1.5
Weighted average shares - diluted									46.8	51.2	54.2
Earnings per common share:
Basic (in dollars per share)	$ 2.61	$ 3.75	$ 4.65	$ 5.19	$ 2.29	$ 10.20	$ 2.15	$ (0.36)	$ 16.29	$ 14.17	$ 7.06
Diluted (in dollars per share)	$ 2.43	$ 3.50	$ 4.39	$ 4.84	$ 2.10	$ 9.24	$ 1.91	$ (0.36)	$ 15.25	$ 12.72	$ 6.28
Stock options and warrants excluded from calculation									5.2	3.8	9.3

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details)	12 Months Ended
	Dec. 31, 2016itemshares	Dec. 31, 2015shares
Equity Incentive Plan
Number of Equity Incentive Plans | item	2
Amended and Restated Equity Incentive Plan (The 1999 Plan)
Equity Incentive Plan
Granted (in shares)	0
Stock Incentive Plan 2015 (The 2015 Plan)
Equity Incentive Plan
Maximum number of shares authorized to be issued	6,150,000
Granted (in shares)	1,600,000	200,000
Stock Options
Equity Incentive Plan
Granted (in shares)	1,630,552
Expected volatility maximum period	5 years

Stockholders' Equity - Assumpti

Stockholders' Equity - Assumptions for Stock Options (Details) - Stock Options	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Method and assumptions on valuation of stock options
Expected volatility (as a percent)	34.80%	33.10%	32.60%
Risk-free interest rate (as a percent)	1.60%	2.00%	1.70%
Expected term of options (in years)	5 years 9 months 18 days	5 years 9 months 18 days	5 years
Expected forfeiture rate (as a percent)	5.40%	1.50%	0.00%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options Status and Activity (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock option activity
Outstanding at the beginning of the period (in shares)	3,247,438
Granted (in shares)	1,630,552
Exercised (in shares)	(243,624)	(985,583)	(1,462,369)
Forfeited (in shares)	(175,075)
Outstanding at the end of the period (in shares)	4,459,291	3,247,438
Exercisable at the end of the year (in shares)	3,231,814
Expected to vest at the end of the year (in shares)	1,150,003
Options disclosures
Outstanding at the beginning of the period (in dollars per share)	$ 93.09
Granted (in dollars per share)	119.38
Exercised (in dollars per share)	31.71
Forfeited (in dollars per share)	120.79
Outstanding at the end of the period (in dollars per share)	104.97	$ 93.09
Exercisable at the end of period (in dollars per share)	99.46
Expected to vest at the end of period (in dollars per share)	$ 119.35
Employee stock options, Weighted Average Remaining Contractual Term (in Years)
Outstanding at the end of the period	7 years
Exercisable at the end of the period	6 years 1 month 6 days
Expected to vest at the end of the period	9 years 2 months 12 days
Employee stock options, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 176.7
Exercisable at the end of the period (in dollars)	147.1
Expected to vest at the end of period (in dollars)	$ 27.9
Weighted average grant date fair value of stock options (in dollars per share)	$ 42.59	$ 60.70	$ 40.70
Aggregate grant date fair value	$ 19.9	$ 0	$ 29.5

Stockholders' Equity - Share-Ba

Stockholders' Equity - Share-Based Compensation Expense (Details) - Stock Options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based compensation expense
Share-based compensation expense before tax	$ 24.8	$ 4.9	$ 29.5
Related income tax benefit	(9.1)	(1.8)	(10.4)
Share-based compensation (benefit) expense, net of tax	15.7	3.1	19.1
Unrecognized compensation cost	$ 39.2
Recognition of share-based compensation expense (in years)	3 years 2 months 12 days
Cost of product sales
Share-based compensation expense
Share-based compensation expense before tax	$ 0.5
Research and development
Share-based compensation expense
Share-based compensation expense before tax	1.4
Selling, general and administrative
Share-based compensation expense
Share-based compensation expense before tax	22.9	$ 4.9	$ 29.5
Selling, general and administrative | Corporate officer
Share-based compensation expense
Share-based compensation expense before tax	$ 9.8

Stockholders' Equity - Stock 68

Stockholders' Equity - Stock Options Exercise Data (Details) - Stock Options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of stock option exercise data
Number of options exercised (in shares)	243,624	985,583	1,462,369
Cash received from options exercised	$ 7.7	$ 39.3	$ 50.2
Total intrinsic value of options exercised	21.9	120.3	108.4
Tax benefits realized from options exercised	$ 5.9	$ 37.4	$ 30.8

Stockholders' Equity - Restrict

Stockholders' Equity - Restricted Stock Units (Details) - Restricted stock units $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)item$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock entitled for each unit upon vesting | item	1
Granted (in shares) | shares	20,960
Awards granted during the period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 101.80
Aggregate grant date fair value	$ 2.1
Share-based compensation expense before tax	$ 1.1
Recognition of share-based compensation expense (in years)	6 months
June 2016 Award Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 1

Stockholders' Equity - Employee

Stockholders' Equity - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan (ESPP)	1 Months Ended
	Jun. 30, 2012shares
Share-based compensation expense
Offering period (in months)	6 months
Maximum percentage of compensation employees may contribute for ESPP (in percentage)	15.00%
Percentage of the lower of the fair market value of common stock on the first or last trading day of a given offering period (in percentage)	85.00%
Maximum number of shares each eligible employees may purchase in any given offering period (in shares)	4,000
Term of ESPP (in years)	20 years
Maximum number of shares authorized to be issued (in shares)	3,000,000

Stockholders' Equity - Share Re

Stockholders' Equity - Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 31, 2015	Jun. 30, 2014
Share Repurchase
Period over which shares may be purchased under share repurchase program			1 year
Cost of shares repurchased	$ 500	$ 394.5	$ 483.1
2014 Share Repurchase Program
Share Repurchase
Authorized aggregate repurchases of common stock					$ 500
Repurchased shares of common stock		2.4	0.9
Cost of shares repurchased		$ 394.5	$ 105.5
2015 Share Repurchase Program
Share Repurchase
Authorized aggregate repurchases of common stock				$ 500
Repurchased shares of common stock	4.2
Cost of shares repurchased	$ 500

Stockholders' Equity - Sharehol

Stockholders' Equity - Shareholder Rights Plan (Details)	Jun. 30, 2008item$ / item
Shareholder Rights Plan
Purchase price of each Right, before the amendment and restatement of the Rights (in dollars per one one-thousandth of a share)	64.75
Purchase price of each Right, after the amendment and restatement of the Rights (in dollars per one one-thousandth of a share)	400
Number of shares of Series A Junior Participating Preferred Stock each Right entitles a holder to purchase | item	0.001
Minimum ownership percentage in the outstanding shares of voting stock from the commencement of a tender offer that would result in the exercise of shares under one condition of the Agreement (as a percent)	15.00%

Accumulated Other Comprehensi73

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in accumulated other comprehensive income (loss), net of tax
Balance	$ 1,588.6	$ 1,242.5	$ 1,259.4
Other comprehensive income (loss), net of tax	3.6	(3.7)	(3.6)
Balance	1,851.3	1,588.6	1,242.5
Accumulated Other Comprehensive Loss
Changes in accumulated other comprehensive income (loss), net of tax
Balance	(20.4)	(16.7)	(13.1)
Other comprehensive income (loss) before reclassifications	3	(4.6)
Amounts reclassified from accumulated other comprehensive gain	0.6	0.9
Other comprehensive income (loss), net of tax	3.6	(3.7)
Balance	(16.8)	(20.4)	(16.7)
Defined Benefit Pension Plan
Changes in accumulated other comprehensive income (loss), net of tax
Balance	(5.3)	(6.9)
Other comprehensive income (loss) before reclassifications	6	0.7
Amounts reclassified from accumulated other comprehensive gain	0.6	0.9
Other comprehensive income (loss), net of tax	6.6	1.6
Balance	1.3	(5.3)	(6.9)
Foreign Currency Translation Losses
Changes in accumulated other comprehensive income (loss), net of tax
Balance	(15.1)	(9.8)
Other comprehensive income (loss) before reclassifications	(3)	(5.3)
Other comprehensive income (loss), net of tax	(3)	(5.3)
Balance	$ (18.1)	$ (15.1)	$ (9.8)

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 311.9	$ 351.2	$ 166.4
State	24.1	37	21.4
Total current	336	388.2	187.8
Deferred
Federal	8.3	(2.7)	(3.1)
State	2.2	7.3	0.4
Total deferred	10.5	4.6	(2.7)
Total income tax expense	$ 346.5	$ 392.8	$ 185.1

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of income taxes
Federal tax rate (as a percent)	35.00%
Federal taxes at 35%	$ 371.1	$ 365.5	$ 183.8
State taxes, net of federal benefit	17.1	28.7	12.9
General business credits	(10.5)	(6.9)	(12.2)
Section 199 deduction	(22)	(21.8)	(11.7)
Nondeductible compensation expense	(11.4)	29.3	13
Other	2.2	(2)	(0.7)
Total income tax expense	$ 346.5	$ 392.8	$ 185.1

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Tax Asset (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Intangible assets	$ 48.1	$ 53.4
Nonqualified stock options	44.7	37.4
SERP	18.9	17.1
STAP awards	80.1	95.2
Other	22.9	27.4
Total deferred tax assets	214.7	230.5
Deferred tax liabilities:
Plant and equipment principally due to differences in depreciation	(23.5)	(26.5)
Other	(8.2)	(7.9)
Net deferred tax asset before valuation allowance	183	196.1
Valuation allowance	(4.7)	(3.4)
Net deferred tax assets	178.3	$ 192.7
Undistributed earnings of foreign operations	$ 13

Income Taxes - Reconciliation77

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of beginning and ending balances of unrecognized tax benefits
Beginning balance of unrecognized tax benefits	$ 0.5	$ 1.4
Lapse of statute of limitations	0	(0.9)
Ending balance of unrecognized tax benefits	0.5	0.5
Positions of uncertain tax, if realized, would impact the effective tax rate	0.3	0.3
Accrued interest expense	0	$ 0
Federal
Reconciliation of beginning and ending balances of unrecognized tax benefits
Net operating loss carryforwards	0
State
Reconciliation of beginning and ending balances of unrecognized tax benefits
Net operating loss carryforwards	$ 55

Employee Benefit Plans - SERP -

Employee Benefit Plans - SERP - General (Details) - Supplemental Executive Retirement Plan (SERP) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Executive Retirement Plan Disclosure
Eligibility age		60 years
Number of months of salary taken as gross base for receipt of monthly payments		36 months
Vesting period of plan, when participants begin receiving payments		6 months
Reconciliation of beginning and ending balances of the projected benefit obligation
Projected benefit obligation at the beginning of the year		$ 54.8	$ 58
Service cost		2.7	3.5	$ 5.5
Interest cost		1.5	1.8	2.4
Plan amendments		2
Benefits paid			(7.1)
Actuarial gain		(11.5)	(1.4)
Projected benefit obligation at the end of the year		49.5	54.8	$ 58
Unfunded at end of the year		49.5	54.8
Amount included in Other current liabilities		$ 15.2	$ 14.7
Increase (reduction) in benefit obligation due to departure of certain participants	$ (7.1)
Discount Rate (as a percent)	3.36%	3.67%	3.82%
Accumulated benefit obligation		$ 37.5	$ 42.3
Future estimated benefit payments
2,017		15.2
2,019		7.2
Thereafter		65.6
Total future estimated benefit payments		$ 88

Employee Benefit Plans - SERP79

Employee Benefit Plans - SERP - Assumptions and Components of Net Periodic Pension Cost (Details) - Supplemental Executive Retirement Plan (SERP)	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Weighted-average assumptions used to measure SERP obligation:
Discount Rate (as a percent)	3.67%	3.36%	3.82%
Salary Increases (as a percent)	4.00%		4.00%

Employee Benefit Plans - SERP80

Employee Benefit Plans - SERP - Components of Net Periodic Pension Cost (Details) - Supplemental Executive Retirement Plan (SERP) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net periodic pension cost
Service cost	$ 2.7	$ 3.5	$ 5.5
Interest cost	1.5	1.8	2.4
Amortization of prior service cost	1.4	1.2	1.2
Amortization of net actuarial (gain) loss	(0.4)	0.2	0.2
Total	$ 5.2	$ 6.7	$ 9.3

Employee Benefit Plans - SERP81

Employee Benefit Plans - SERP - Reclassifications from AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Prior service cost	$ 1.4	$ 1.2
Amortization of net actuarial (gain) loss	(0.4)	0.2
Total prior service cost and amortization of net actuarial (gain) loss	1	1.4
Tax benefit	(0.4)	(0.5)
Total, net of tax	0.6	0.9
Research and development
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Prior service cost	0.3	0.4
Amortization of net actuarial (gain) loss	(0.1)
Selling, general and administrative
Reclassifications related to the SERP from accumulated other comprehensive loss to the statement of operations
Prior service cost	1.1	0.8
Amortization of net actuarial (gain) loss	$ (0.3)	$ 0.2

Employee Benefit Plans - SERP82

Employee Benefit Plans - SERP - Other (Details) - Supplemental Executive Retirement Plan (SERP) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amounts relating to the SERP that have been recognized in other comprehensive gain (loss)
Net unrecognized actuarial gain	$ 11	$ 1.6	$ 5
Net unrecognized prior service (benefit) cost	(0.6)	1.2	(2.6)
Total	10.4	2.8	2.4
Tax benefit	(3.8)	(1.2)	(0.9)
Total, net of tax	6.6	1.6	1.5
Accumulated other comprehensive income (loss) that have not yet been recognized as a component of net periodic pension cost
Net unrecognized actuarial (gain) loss	(9.8)	1.2	2.8
Net unrecognized prior service cost	7.7	7.1	8.3
Total	(2.1)	8.3	11.1
Tax expense (benefit)	0.8	(3)	(4.2)
Total, net of tax	(1.3)	$ 5.3	$ 6.9
Amounts included in accumulated other comprehensive income expected to be recognized as components of net periodic pension expense
Amortization of prior service cost	1.5
Amortization of net actuarial gain	(0.6)
Total	$ 0.9

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Retirement Plan (Details)	12 Months Ended
	Dec. 31, 2016item
Employee Retirement Plan
Employer's matching contribution, percentage of participant's elected salary deferral	40.00%
Period of service for vesting of matching contributions	3 years
Annual increments for vesting in employer's matching contribution	0.33
Period over which the matching contribution vest annually	3 years

Assignment and License Agreem84

Assignment and License Agreements (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Nov. 30, 2008	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2009	Dec. 31, 2007	Dec. 31, 1997	Dec. 31, 2015
Assignment and License Agreements
Common stock issued (in shares)					69,340,985				68,987,919
GlaxoSmithKline PLC (Glaxo) | Treprostinil
Assignment and License Agreements
Minimum term of royalty payment								10 years
Supernus Pharmaceuticals, Inc. | Orenitram
Assignment and License Agreements
Minimum term of royalty payment				12 years
Scaling royalties percentage					single digit
Eli Lilly and Company | Adcirca
Assignment and License Agreements
Royalty as a percentage of net sales			5.00%
Scripps Research Institute | Unituxin
Assignment and License Agreements
Royalty as a percentage of net sales		1.00%
Toray
Assignment and License Agreements
Common stock issued (in shares)							200,000
Common stock issued shares split							400,000
Price per share (in dollars per share)							$ 27.21
Notice period							30 days
Non-refundable payments to be made under the license	$ 50
Term of installment payments under license	5 years
Medtronic Inc | Remodulin
Assignment and License Agreements
Royalty as a percentage of net sales						10.00%
DEKA Research & Development Corp | Remodulin
Assignment and License Agreements
Scaling royalties percentage					single-digit

Distribution Agreements (Detail

Distribution Agreements (Details)	12 Months Ended
	Dec. 31, 2016item
Distribution Agreements
Number of distributors	2
United States | Remodulin and Tyvaso and Orenitram
Distribution Agreements
Distribution agreement, initial term	1 year
Distribution agreement, automatically renew terms	1 year
Product concentration | United States | Net revenues | Remodulin and Tyvaso and Orenitram
Distribution Agreements
Number of distributors	2

Segment Information - General (

Segment Information - General (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									$ 1,598.8	$ 1,460.6	$ 1,279.5
Cost of product sales	$ 28.4	$ 23.6	$ 20	$ 0.7	$ 25.3	$ 6.9	$ 16	$ 20.8	72.7	69	125.9
Gross profit									$ 1,526.1	1,391.6	1,153.6
Number of operating segments | segment									1
Remodulin
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									$ 602.3	572.8	553.7
Cost of product sales									10.5	12.4	47.3
Gross profit									591.8	560.4	506.4
Tyvaso
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									404.6	470.1	463.1
Cost of product sales									19.6	23.9	57.5
Gross profit									385	446.2	405.6
Adcirca
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									372.2	278.8	221.5
Cost of product sales									21.4	16.5	13.5
Gross profit									350.8	262.3	208
Orenitram
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									157.2	118.4	41.2
Cost of product sales									13.7	12.5	7.6
Gross profit									143.5	105.9	$ 33.6
Unituxin
Net Product Sales, Cost Of Product Sales, And Gross Profit By Product [Line Items]
Net product sales									62.5	20.5
Cost of product sales									7.5	3.7
Gross profit									$ 55	$ 16.8

Segment Information - Geographi

Segment Information - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net revenues to external customers and long-lived assets located by geographic area
Total revenues	$ 409	$ 408.2	$ 412.6	$ 369	$ 404.9	$ 386.2	$ 347.2	$ 327.5	$ 1,598.8	$ 1,465.8	$ 1,288.5
Other revenue										5.2	9
Long-lived assets by geographic area	489.3				495.8				489.3	495.8	478.4
United States
Net revenues to external customers and long-lived assets located by geographic area
Total revenues									1,461.9	1,353	1,180.8
Long-lived assets by geographic area	481.1				481.2				481.1	481.2	462.4
Rest-of-World
Net revenues to external customers and long-lived assets located by geographic area
Total revenues									136.9	112.8	107.7
Long-lived assets by geographic area	$ 8.2				$ 14.6				$ 8.2	$ 14.6	$ 16

Segment Information - Concentra

Segment Information - Concentration Risk (Details) - item	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Information
Number of Distributors	2
Net revenues | Customer concentration | Customer one
Segment Information
Concentration risk, percentage	50.00%	55.00%	58.00%
Net revenues | Customer concentration | Customer two
Segment Information
Concentration risk, percentage	14.00%	16.00%	15.00%

Quarterly Financial Informati89

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total revenues	$ 409	$ 408.2	$ 412.6	$ 369	$ 404.9	$ 386.2	$ 347.2	$ 327.5	$ 1,598.8	$ 1,465.8	$ 1,288.5
Cost of product sales	28.4	23.6	20	0.7	25.3	6.9	16	20.8	72.7	69	125.9
Gross profit	380.6	384.6	392.6	368.3	379.6	379.3	331.2	306.7
Net income (loss)	$ 110.3	$ 161.8	$ 206.1	$ 235.5	$ 104.6	$ 464.4	$ 99.2	$ (16.6)	$ 713.7	$ 651.6	$ 340.1
Net income (loss) per share-basic (in dollars per share)	$ 2.61	$ 3.75	$ 4.65	$ 5.19	$ 2.29	$ 10.20	$ 2.15	$ (0.36)	$ 16.29	$ 14.17	$ 7.06
Net income (loss) per share-diluted (in dollars per share)	$ 2.43	$ 3.50	$ 4.39	$ 4.84	$ 2.10	$ 9.24	$ 1.91	$ (0.36)	$ 15.25	$ 12.72	$ 6.28
Proceeds from Sale of Intangible Assets						$ 350				$ 350
Share tracking award plans (STAP)
Share-based compensation expense charged to operating expenses, net of tax	$ 64.2	$ 28.7	$ (7)	$ (95.5)	$ 73.9	$ (75.7)	$ 27.5	$ 145	$ (9.6)	$ 170.7	$ 102.9

Litigation (Details)

Litigation (Details) - Pending Litigation	12 Months Ended
	Dec. 31, 2016patent
Watson Laboratories Inc.
Litigation
Maximum period for which the FDA is automatically precluded from approving ANDA	30 months
Number of additional patents being addressed in litigation.	2
Actavis Laboratories FL, Inc.
Litigation
Maximum period for which the FDA is automatically precluded from approving ANDA	30 months
Number of patents on which district court decision is adverse	8
SteadyMed Ltd.
Litigation
Number of days for supply of treprostinil under FDA approval	2 days

Schedule II-Valuation and Qua91

Schedule II-Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in valuation and qualifying accounts
Balance at Beginning of Year	$ 3.4
Balance at End of Year	4.7	$ 3.4
Valuation Allowance on Deferred Tax Assets
Change in valuation and qualifying accounts
Balance at Beginning of Year	3.4	3	$ 2.5
Additions Charged to Expense	1.3	0.4	0.5
Balance at End of Year	4.7	3.4	3
Reserve for Inventory Obsolescence
Change in valuation and qualifying accounts
Balance at Beginning of Year	12.1	10.5	18.3
Additions Charged to Expense	8.2	7.9	3.4
Deductions	(2.8)	(6.3)	(11.2)
Balance at End of Year	$ 17.5	$ 12.1	$ 10.5