United Therapeutics (UTHR) 10-Q 30 Oct 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 23, 2019
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	0-26301
Entity Registrant Name	United Therapeutics Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-1984749
Entity Address, Address Line One	1040 Spring Street
Entity Address, City or Town	Silver Spring
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20910
City Area Code	301
Local Phone Number	608-9292
Security 12b Title	Common Stock, par value $0.01 per share
Trading Symbol	UTHR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		43,881,350
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001082554
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 719.7	$ 669.2
Marketable investments	850.3	746.7
Accounts receivable, no allowance for 2019 and 2018	183.6	175.7
Inventories, net	94.1	101
Other current assets	85.7	75.4
Total current assets	1,933.4	1,768
Marketable investments	730.4	442.6
Goodwill and other intangible assets, net	158.4	170.8
Property, plant and equipment, net	678.3	699.7
Deferred tax assets, net	268.1	95.7
Other non-current assets	231	224.2
Total assets	3,999.6	3,401
Current liabilities:
Accounts payable and accrued expenses	161.1	166.1
Line of credit (current)	250
Share tracking awards plan	18.3	72.2
Other current liabilities	40.5	38.3
Total current liabilities	469.9	276.6
Line of credit (non-current)	750	250
Other non-current liabilities	63.9	66.6
Total liabilities	1,283.8	593.2
Commitments and contingencies
Temporary equity		19.2
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 70,499,819 and 70,207,581 shares issued, and 43,880,603 and 43,588,365 shares outstanding at September 30, 2019 and December 31, 2018, respectively	0.7	0.7
Additional paid-in capital	2,025.8	1,940.2
Accumulated other comprehensive loss	(4.1)	(7.9)
Treasury stock, 26,619,216 shares at September 30, 2019 and December 31, 2018	(2,579.2)	(2,579.2)
Retained earnings	3,272.6	3,434.8
Total stockholders' equity	2,715.8	2,788.6
Total liabilities and stockholders' equity	3,999.6	3,401
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	Sep. 30, 2019	Dec. 31, 2018
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	70,499,819	70,207,581
Common stock, shares outstanding	43,880,603	43,588,365
Treasury stock, shares	26,619,216	26,619,216
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	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 401.5	$ 412.7	$ 1,137.7	$ 1,246.4
Operating expenses:
Cost of product sales	33	51.9	88.8	166.8
Research and development	85.7	101.1	1,069	219.1
Selling, general and administrative	99.4	110.1	231	186.6
Total operating expenses	218.1	263.1	1,388.8	572.5
Operating income (loss)	183.4	149.6	(251.1)	673.9
Interest income	12.1	7.9	32.7	19.9
Interest expense	(11.7)	(4.1)	(34.2)	(9.6)
Other (expense) income, net	(16.9)	(0.9)	19.3	(4.8)
Impairment of investment in privately-held company		(12.4)		(12.4)
Total other (expense) income, net	(16.5)	(9.5)	17.8	(6.9)
Income (loss) before income taxes	166.9	140.1	(233.3)	667
Income tax (expense) benefit	(34.5)	(33.6)	76.2	(143.1)
Net income (loss)	$ 132.4	$ 106.5	$ (157.1)	$ 523.9
Net income (loss) per common share:
Basic (in dollars per share)	$ 3.02	$ 2.44	$ (3.59)	$ 12.04
Diluted (in dollars per share)	$ 3.01	$ 2.42	$ (3.59)	$ 11.91
Weighted average number of common shares outstanding:
Basic (in shares)	43.9	43.6	43.8	43.5
Diluted (in shares)	44	44	43.8	44
Net product sales
Revenues:
Total revenues	$ 401.5	$ 412.7	$ 1,137.7	$ 1,246.4

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Comprehensive income:
Net income (loss)	$ 132.4	$ 106.5	$ (157.1)	$ 523.9
Defined benefit pension plan:
Actuarial loss arising during period, net of tax			(0.6)
Amortization of actuarial gain and prior service cost included in net periodic pension cost, net of tax	(0.1)	0.4	(1.6)	1
Total defined benefit pension plan, net of tax	(0.1)	0.4	(2.2)	1
Unrealized gain (loss) on available-for-sale securities, net of tax	1	(0.7)	6	(3.6)
Other comprehensive income (loss), net of tax	0.9	(0.3)	3.8	(2.6)
Comprehensive income (loss)	$ 133.3	$ 106.2	$ (153.3)	$ 521.3

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, 2017	$ 0.7	$ 1,854.3	$ (19.6)	$ (2,579.2)	$ 2,845.6	$ 2,101.8
Balance (in shares) at Dec. 31, 2017	69.9
Increase (Decrease) in Stockholders' Equity
Net income (loss)					523.9	523.9
Unrealized gain (loss) on available-for-sale securities			(3.6)			(3.6)
Defined benefit pension plan			1			1
Shares issued under employee stock purchase plan		3.9				3.9
Exercise of stock options		15.5				15.5
Exercise of stock options (in shares)	0.3
Share-based compensation		50.3				50.3
Balance at Sep. 30, 2018	$ 0.7	1,924	(22.2)	(2,579.2)	3,369.5	2,692.8
Balance (in shares) at Sep. 30, 2018	70.2
Balance at Jun. 30, 2018	$ 0.7	1,903	(21.9)	(2,579.2)	3,263	2,565.6
Balance (in shares) at Jun. 30, 2018	70.2
Increase (Decrease) in Stockholders' Equity
Net income (loss)					106.5	106.5
Unrealized gain (loss) on available-for-sale securities			(0.7)			(0.7)
Defined benefit pension plan			0.4			0.4
Shares issued under employee stock purchase plan		1.8				1.8
Exercise of stock options		0.6				0.6
Share-based compensation		18.6				18.6
Balance at Sep. 30, 2018	$ 0.7	1,924	(22.2)	(2,579.2)	3,369.5	2,692.8
Balance (in shares) at Sep. 30, 2018	70.2
Balance at Dec. 31, 2018	$ 0.7	1,940.2	(7.9)	(2,579.2)	3,434.8	2,788.6
Balance (in shares) at Dec. 31, 2018	70.2
Increase (Decrease) in Stockholders' Equity
Net income (loss)					(157.1)	(157.1)
Unrealized gain (loss) on available-for-sale securities			6			6
Defined benefit pension plan			(2.2)			(2.2)
Shares issued under employee stock purchase plan		4.1				4.1
Restricted stock units withheld for taxes		(2.1)				(2.1)
Common stock issued upon RSU vesting (in shares)	0.1
Exercise of stock options		9.9				9.9
Exercise of stock options (in shares)	0.2
Share-based compensation		63				63
Cumulative effect of accounting change					(5.1)	(5.1)
Reclassification from temporary equity to permanent equity		10.8				10.8
Deconsolidation of variable interest entity		(0.1)				(0.1)
Balance at Sep. 30, 2019	$ 0.7	2,025.8	(4.1)	(2,579.2)	3,272.6	2,715.8
Balance (in shares) at Sep. 30, 2019	70.5
Balance at Jun. 30, 2019	$ 0.7	2,001.7	(5)	(2,579.2)	3,140.2	2,558.4
Balance (in shares) at Jun. 30, 2019	70.5
Increase (Decrease) in Stockholders' Equity
Net income (loss)					132.4	132.4
Unrealized gain (loss) on available-for-sale securities			1			1
Defined benefit pension plan			(0.1)			(0.1)
Shares issued under employee stock purchase plan		1.9				1.9
Restricted stock units withheld for taxes		(0.2)				(0.2)
Share-based compensation		22.5				22.5
Deconsolidation of variable interest entity		(0.1)				(0.1)
Balance at Sep. 30, 2019	$ 0.7	$ 2,025.8	$ (4.1)	$ (2,579.2)	$ 3,272.6	$ 2,715.8
Balance (in shares) at Sep. 30, 2019	70.5

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) $ in Millions	Sep. 30, 2019USD ($)$ / sharesshares
Common stock subject to repurchase | $	$ 10.8
Temporary equity common stock subject to repurchase
Common stock issued (in shares)	200,000
Common stock issued split (in shares)	400,000
Repurchase price (in dollars per share) | $ / shares	$ 27.21

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net (loss) income	$ (157.1)	$ 523.9
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	33.4	25.4
Share-based compensation expense (benefit)	15.9	(29.2)
Impairment of investment in privately-held company		12.4
Deconsolidation of variable interest entity	2
Intangible asset impairment charges	8.8
Asset impairment charges	8.4
Other	(27.9)	4.4
Impairment write downs	8.4
Changes in operating assets and liabilities:
Accounts receivable	(7.8)	81.9
Inventories	10.5	4.2
Accounts payable and accrued expenses	(4.9)	21.9
Other assets and liabilities	(190.4)	48.1
Net cash (used in) provided by operating activities	(309.1)	693
Cash flows from investing activities:
Purchases of property, plant and equipment	(59)	(132.6)
Decrease in cash due to deconsolidation of variable interest entity	(12.5)
Deposits	(5.6)	(33)
Purchases of held-to-maturity and other investments		(63.4)
Sales/maturities of held-to-maturity investments	39.7	53
Purchases of available-for-sale investments	(974.7)	(618.5)
Sales/maturities of available-for-sale investments	618.5	175.2
Purchase of investments in privately-held companies	(8)	(5)
Acquisition, net of cash acquired		(124.1)
Net cash used in investing activities	(401.6)	(748.4)
Cash flows from financing activities:
Proceeds from line of credit	800	250
Repayment of line of credit	(50)	(250)
Payments of debt issuance costs	(0.7)	(13.2)
Proceeds from the exercise of stock options	(9.9)	(15.5)
Proceeds from the issuance of stock under employee stock purchase plan	4.1	3.9
Restricted stock units withheld for taxes	(2.1)
Net cash provided by financing activities	761.2	6.2
Effect of exchange rate changes on cash and cash equivalents		0.1
Net increase in cash and cash equivalents	50.5	(49.1)
Net increase in cash and cash equivalents	50.5	(49.1)
Cash and cash equivalents, beginning of period	669.2	705.1
Cash and cash equivalents, end of period	719.7	656
Supplemental cash flow information:
Cash paid for interest	31.7	6.9
Cash paid for income taxes	94.4	52.1
Non-cash investing and financing activities:
Non-cash additions to property, plant and equipment	$ 3.9	$ 18.2

Organization and Business Descr

Organization and Business Description	9 Months Ended
	Sep. 30, 2019
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 ® ® ® ® ® As used in these notes to our 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.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Basis of Presentation
Basis of Presentation	2. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with the rules and regulations of the U.S. Securities and Exchange Commission (SEC) for interim financial information. Accordingly, they do not include all of the information required by U.S. generally accepted accounting principles (GAAP) for complete financial statements. These consolidated financial statements should be read in conjunction with our audited consolidated financial statements and the accompanying notes to our consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2018, as filed with the SEC on February 27, 2019. In our management’s opinion, the accompanying consolidated financial statements contain all adjustments, including normal, recurring adjustments, necessary to fairly present our financial position as of September 30, 2019 and December 31, 2018, our statements of operations, comprehensive income, and stockholders’ equity for the three- and nine-month periods ended September 30, 2019 and 2018 and our statements of cash flows for the nine-month periods ended September 30, 2019 and 2018. Interim results are not necessarily indicative of results for an entire year. In our statements of cash flows, we reclassified the prior period deposits within the “cash flows from operating activities” section to “cash flows from investing activities” section to conform with the current period presentation. Recently Issued Accounting Standards Accounting Standards Adopted During the Period In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Leases (Topic 842)—Targeted Improvements Upon adoption of this standard, we recognized a right-of-use asset of $8.2 million, and a corresponding lease liability of the same amount, related to our operating leases as of January 1, 2019. In addition, we recognized a cumulative-effect adjustment for the de-recognition of our build-to-suit leases as these leases no longer qualify for build-to-suit accounting and have instead been recognized as operating leases under ASC 842. The adjustment resulted in a decrease to retained earnings of $5.1 million, which is net of a tax benefit. At adoption, our weighted-average remaining lease term was 3.0 years and our weighted-average discount rate was 4.9%. Supplemental balance sheet information related to operating leases was as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial Statement Line Item on our September 30, January 1, Operating Leases ​ Consolidated Balance Sheets ​ 2019 ​ 2019 Right-of-use assets Other non-current assets ​ $ 4.7 ​ $ 8.2 Current lease liabilities Other current liabilities ​ $ 1.9 ​ $ 4.1 Non-current lease liabilities Other non-current liabilities ​ 2.8 ​ 4.1 Total operating lease liabilities ​ $ 4.7 ​ $ 8.2 ​ We recorded $1.2 million and $3.9 million in operating lease expense for the three and nine months ended September 30, 2019 and recorded $1.0 million and $3.2 million in operating lease expense for the three and nine months ended September 30, 2018. The amounts recorded in operating lease expense include short-term leases and variable lease costs, which are immaterial. In connection with completion of construction in the third quarter of 2019 of a building we own, we leased part of the space in the building to another entity as part of a broader collaboration arrangement. The lease is accounted for as a sales-type lease. Upon lease commencement in the third quarter of 2019, we reclassified $23.1 million of property, plant and equipment, net to other non-current assets on our consolidated balance sheets. The collaboration arrangement activity was immaterial for the period ended September 30, 2019. In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, to eliminate or modify certain disclosure rules that are redundant, outdated, or duplicative of U.S. GAAP or other regulatory requirements. Among other changes, the amendments eliminated the annual requirement to disclose the high and low trading prices of our common stock. In addition, the amendments expanded the disclosure requirements related to the analysis of shareholders’ equity for interim financial statements. An analysis of the changes in each caption of shareholders’ equity presented in the balance sheet must be provided in a note or separate statement, and we have provided this disclosure in a separate statement (Consolidated Statements of Stockholders’ Equity) beginning in the first quarter of 2019. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other: Simplifying the Test for Goodwill Impairment In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Topic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans

Investments

Investments	9 Months Ended
	Sep. 30, 2019
Investments
Investments	3. Investments Available-for-Sale Debt Securities Available-for-sale debt securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income in stockholders’ equity, until realized. Available-for-sale debt securities consisted of the following (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair As of September 30, 2019 Cost ​ Gains Losses Value U.S. government and agency securities ​ $ 1,287.9 ​ $ 3.2 ​ $ (0.5) ​ $ 1,290.6 Corporate debt securities ​ ​ 223.6 ​ ​ 1.8 ​ ​ (0.1) ​ ​ 225.3 Total ​ $ 1,511.5 ​ $ 5.0 ​ $ (0.6) ​ $ 1,515.9 Reported under the following captions on our consolidated balance sheet: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 785.5 Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 730.4 Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,515.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair As of December 31, 2018 Cost ​ Gains Losses Value U.S. government and agency securities ​ $ 1,077.4 ​ $ 0.7 ​ $ (3.9) ​ $ 1,074.2 Corporate debt securities ​ ​ 72.3 ​ ​ — ​ ​ (0.3) ​ ​ 72.0 Total ​ $ 1,149.7 ​ $ 0.7 ​ $ (4.2) ​ $ 1,146.2 Reported under the following captions on our consolidated balance sheet: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 705.8 Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 440.4 Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,146.2 ​ The following table summarizes the contractual maturities of available-for-sale marketable investments (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ Amortized Fair ​ Cost Value Due within one year ​ $ 784.7 ​ $ 785.5 Due in one to three years ​ ​ 726.8 ​ ​ 730.4 Total ​ $ 1,511.5 ​ $ 1,515.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ Amortized Fair ​ Cost Value Due within one year ​ $ 708.2 ​ $ 705.8 Due in one to three years ​ 441.5 ​ ​ 440.4 Total ​ $ 1,149.7 ​ $ 1,146.2 ​ Investments in Privately-Held Companies As of September 30, 2019, we maintained non-controlling equity investments in privately-held companies of $101.7 million in the aggregate. We measure these investments using the measurement alternative because the fair values of these investments are not readily determinable. Under this alternative, the investments are measured at cost, less any impairment, adjusted for any observable price changes. There were no impairments or observable price changes in our investments in privately-held companies during the three and nine months ended September 30, 2019. We include our investments in privately-held companies within other non-current assets on our consolidated balance sheets. These investments are subject to a periodic impairment review and if impaired, the investment is measured and recorded at fair value in accordance with ASC 820, Fair Value Measurements During the quarter ended September 30, 2018, one of the privately-held companies in which we invested underwent a significant change in management and a change in business outlook and strategy, all of which triggered our review of the recoverability of our investment in the company. We determined the fair value of our investment as of September 30, 2018 considering an income approach based on the company's discounted projected cash flows. We corroborated the implied revenue multiples from the income approach with the observed revenue multiples of comparable public companies. We concluded that the fair value of our investment as of September 30, 2018 was lower than its carrying value, resulting in an impairment charge of $12.4 million. Deconsolidation of a Variable Interest Entity In April 2017, we made a $7.5 million minority equity investment in a privately-held company. In addition to our investment, we entered into an exclusive license, development and commercialization agreement (the License Agreement) with this company. The License Agreement entitled us to control rights sufficient to require us to regard the company as a variable interest entity (VIE) and to consolidate the company’s balance sheet and results of operations as the primary beneficiary of this company. In June 2019, we elected to terminate the License Agreement. The termination of the License Agreement caused us to impair an associated in-process research and development (IPR&D) asset during the second quarter of 2019 and recognize an impairment charge of $8.8 million, which is included within research and development expense on our consolidated statements of operations. Upon effectiveness of the termination of the License Agreement in the third quarter of 2019 , we no longer have the power to direct the entity’s activities. Consequently, we deconsolidated the entity in the third quarter of 2019. Our deconsolidation of the entity’s balance sheet, which included $3.5 million of goodwill and $8.4 million of temporary equity, resulted in a net deconsolidation loss of $2.0 million. The deconsolidation loss is included within other (expense) income, net on our consolidated statements of operations . We have no further funding obligations to the entity, and our maximum exposure to loss is equal to the carrying value of our retained interest. We now account for our equity investment in this privately-held company using the equity method of accounting because we have the ability to exercise significant influence over the operating and financial policies of the entity, but we no longer have a controlling financial interest. Investments in Equity Securities with Readily Determinable Fair Values We held investments in equity securities with readily determinable fair values of $64.8 million and $3.5 million as of September 30, 2019 and December 31, 2018, respectively, which are included in current marketable investments on our consolidated balance sheets. During the second quarter of 2019, TransMedics Group, Inc., one of the privately-held companies in which we had invested, completed its initial public offering and its common stock began trading on the Nasdaq Stock Market. As a result, the equity securities we own in this company are now recorded at fair value rather than reflected as an investment in a privately-held company. Changes in the fair value of publicly traded equity securities are recorded on our consolidated statements of operations within other (expense) income, net. Refer to Note 4 —Fair Value Investments

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements We account for certain assets and liabilities at fair value and classify these assets and liabilities within a fair value hierarchy (Level 1, Level 2 or Level 3). Our 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 September 30, 2019 ​ Level 1 Level 2 Level 3 Balance Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 253.4 ​ $ — ​ $ — ​ $ 253.4 Time deposits (2) ​ ​ — ​ ​ 86.9 ​ ​ — ​ ​ 86.9 U.S. government and agency securities (3) ​ ​ — ​ ​ 1,290.6 ​ ​ — ​ ​ 1,290.6 Corporate debt securities (3) ​ — ​ 225.3 ​ — ​ 225.3 Equity securities (4) ​ ​ 64.8 ​ ​ — ​ ​ — ​ ​ 64.8 Total assets ​ $ 318.2 ​ $ 1,602.8 ​ $ — ​ $ 1,921.0 Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (5) ​ — ​ — ​ 13.4 ​ 13.4 Total liabilities ​ $ — ​ $ — ​ $ 13.4 ​ $ 13.4 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ Level 1 Level 2 Level 3 Balance Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 247.6 ​ $ — ​ $ — ​ $ 247.6 Time deposits (2) ​ ​ — ​ ​ 35.9 ​ ​ — ​ ​ 35.9 U.S. government and agency securities (3) ​ ​ — ​ ​ 1,074.2 ​ ​ — ​ ​ 1,074.2 Corporate debt securities (3) ​ — ​ 75.7 ​ — ​ 75.7 Equity securities (4) ​ ​ 3.5 ​ ​ — ​ ​ — ​ ​ 3.5 Total assets ​ $ 251.1 ​ $ 1,185.8 ​ $ — ​ $ 1,436.9 Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (5) ​ — ​ — ​ 13.4 ​ 13.4 Total liabilities ​ $ — ​ $ — ​ $ 13.4 ​ $ 13.4 (1) Included in cash and cash equivalents on our consolidated balance sheets. (2) Included in cash equivalents and current and non-current marketable investments on our 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. (3) Included in cash equivalents and current and non-current marketable investments on our consolidated balance sheets. Refer to Note 3 —Investments—Available-for-Sale Debt Securities for further information. The fair value of these securities is principally measured or corroborated by trade data for identical securities for which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded. (4) Included in current marketable investments on our consolidated balance sheets. The fair value of these securities is based on quoted market prices for identical instruments in active markets. During the three and nine months ended September 30, 2019, we recognized $13.0 million of net unrealized losses and $19.5 million of net unrealized gains, respectively, on these securities and recorded these losses and gains on our consolidated statements of operations within other (expense) income, net. Refer to Note 3 —Investments—Investments in Equity Securities with Readily Determinable Fair Values. (5) Included in non-current liabilities on our consolidated balance sheets. The fair value of contingent consideration has been estimated using probability-weighted discounted cash flow models (DCFs). The DCFs incorporate 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. The change in the fair value of contingent consideration for the three and nine months ended September 30, 2019 was not material. 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 are reported above within the fair value hierarchy. Refer to Note 3 —Investments.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2019
Inventories
Inventories	5. Inventories Inventories are stated at the lower of cost (first-in, first-out method) or net realizable value and consist of the following, net of reserves (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2019 ​ 2018 Raw materials ​ $ 19.3 ​ $ 24.3 Work-in-progress ​ 29.8 ​ 28.0 Finished goods ​ 45.0 ​ 48.7 Total inventories ​ $ 94.1 ​ $ 101.0 ​

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	9 Months Ended
	Sep. 30, 2019
Goodwill and Other Intangible Assets
Goodwill and Other Intangible Assets	6. Goodwill and Other Intangible Assets Goodwill and other intangible assets comprise the following (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ As of December 31, 2018 ​ ​ ​ Accumulated ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Gross ​ Amortization ​ Net ​ Gross ​ Amortization ​ Net Goodwill ​ $ 28.0 ​ $ — ​ $ 28.0 ​ $ 31.5 ​ $ — ​ $ 31.5 Other intangible assets: ​ ​ ​ ​ ​ ​ Technology, patents and trade names ​ 6.7 ​ (5.2) ​ 1.5 ​ 6.7 ​ (5.1) ​ 1.6 In-process research and development ​ 128.9 ​ — ​ 128.9 ​ 137.7 ​ — ​ 137.7 Total ​ $ 163.6 ​ $ (5.2) ​ $ 158.4 ​ $ 175.9 ​ $ (5.1) ​ $ 170.8 ​ In June 2019, we elected to terminate our License Agreement with the VIE discussed under Note 3 —Investments—Deconsolidation of a Variable Interest Entity

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt
Debt	7. Debt Unsecured Revolving Credit Facility - Credit Agreement In June 2018, we entered into a credit agreement (the Credit Agreement) with Wells Fargo Bank, National Association (Wells Fargo), as administrative agent and a swingline lender, and various other lender parties, providing for: (1) an unsecured revolving credit facility of up to $1.0 billion; and (2) a second unsecured revolving credit facility of up to $500.0 million (which facilities may, at our request, be increased by up to $300.0 million in the aggregate subject to obtaining commitments from existing or new lenders for such increase and other conditions). In accordance with the terms of the Credit Agreement, in June 2019, we extended the maturity date of the Credit Agreement by one year, to June 2024. The Credit Agreement provides the lenders the ability to extend the maturity date by one additional year to June 2025 if we request such an extension. At our option, amounts borrowed under the Credit Agreement 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 Credit Agreement). To date, we have elected to calculate interest on the outstanding balance at LIBOR plus an applicable margin. In connection with the Credit Agreement, we incurred debt issuance costs in June 2018 of $13.2 million, $12.6 million of which were capitalized and are being amortized over the term of the Credit Agreement. On June 27, 2018 we borrowed $250.0 million under the Credit Agreement and used the funds to repay outstanding indebtedness under a prior credit agreement. On January 24, 2019, we paid an upfront payment of $800.0 million related to our exclusive license agreement with Arena Pharmaceuticals, Inc. (Arena) and funded the payment by borrowing $800.0 million under the Credit Agreement. On September 30, 2019, we paid down $50.0 million on our revolving credit facility under the Credit Agreement. This brought our aggregate outstanding balance under the Credit Agreement to $1.0 billion as of September 30, 2019. Although our credit facility matures in 2024, we classified $250.0 million of the outstanding balance as a current liability on our consolidated balance sheet as we intend to repay this amount within one year. The Credit Agreement contains customary events of default and customary affirmative and negative covenants. As of September 30, 2019, we were in compliance with these covenants. Lung Biotechnology PBC is our only subsidiary that guarantees our obligations under the Credit Agreement though, from time to time, one or more of our other subsidiaries may be required to guarantee our obligations. During the three and nine months ended September 30, 2019, we recorded $11.7 million and $34.2 million of interest expense, respectively, related to the Credit Agreement. During the three and nine months ended September 30, 2018, we recorded $4.1 million and $9.6 million of interest expense, respectively, related to a prior credit agreement.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2019
Share-Based Compensation
Share-Based Compensation	8. Share-Based Compensation As of September 30, 2019, 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 Amended and Restated 2015 Stock Incentive Plan (as amended to date, the 2015 Plan). The 2015 Plan provides for the issuance of up to 9,500,000 shares of our common stock pursuant to awards granted under the 2015 Plan, which includes the 450,000 shares added pursuant to an amendment and restatement of the 2015 Plan approved by our shareholders in June 2019. No further awards will be granted under the 1999 Plan. We also have one equity incentive plan, the United Therapeutics Corporation 2019 Inducement Stock Incentive Plan (the 2019 Inducement Plan), that has not been approved by our shareholders, as permitted by the Nasdaq Stock Market rules. The 2019 Inducement Plan was approved by our Board of Directors in February 2019 and provides for the issuance of up to 99,000 shares of our common stock under awards granted to newly-hired employees. Currently, we grant equity-based awards to employees and members of our Board of Directors in the form of stock options and restricted stock units under the 2015 Plan, and we grant restricted stock units to newly-hired employees under the 2019 Inducement Plan. Refer to the sections entitled Stock Options Restricted Stock Units We previously issued awards under the United Therapeutics Corporation Share Tracking Awards Plan (2008 STAP) and the United Therapeutics Corporation 2011 Share Tracking Awards Plan (2011 STAP). We refer to the 2008 STAP and the 2011 STAP collectively as the “STAP” and awards outstanding under either of these plans as “STAP awards.” Refer to the section entitled Share Tracking Awards Plans In 2012, our shareholders approved the United Therapeutics Corporation Employee Stock Purchase Plan (ESPP), which is structured to comply with Section 423 of the Internal Revenue Code. Refer to the section entitled Employee Stock Purchase Plan The following table reflects the components of share-based compensation expense (benefit) recognized in our consolidated statements of operations (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Stock options ​ $ 18.4 ​ $ 16.6 ​ $ 52.2 ​ $ 44.8 Restricted stock units ​ 3.8 ​ 2.4 ​ 9.8 ​ 5.3 STAP awards ​ 1.4 ​ 32.2 ​ (47.0) ​ (80.1) Employee stock purchase plan ​ 0.3 ​ 0.2 ​ 0.9 ​ 0.8 Total share-based compensation expense (benefit) before tax ​ $ 23.9 ​ $ 51.4 ​ $ 15.9 ​ $ (29.2) ​ Stock Options We estimate the fair value of stock options using the Black-Scholes-Merton valuation model, which requires us to make certain assumptions that can materially impact the estimation of fair value and related compensation expense. The assumptions used to estimate fair value 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 and the expected dividend yield. The table below includes the weighted-average assumptions used to measure the fair value of all stock options granted during the nine-month periods ended September 30, 2019 and September 30, 2018: ​ ​ ​ ​ ​ ​ ​ ​ September 30, September 30, ​ ​ 2019 2018 ​ Expected volatility 33.8 % 36.2 % Risk-free interest rate 2.4 % 2.7 % Expected term of awards (in years) 5.8 ​ 6.3 ​ Expected dividend yield 0.0 % 0.0 % ​ A summary of the activity and status of stock options under our equity incentive plans during the nine-month period ended September 30, 2019 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted- Average Aggregate ​ ​ ​ Average Remaining ​ Intrinsic ​ ​ Number of ​ Exercise ​ Contractual ​ Value ​ Options Price Term (Years) (in millions) Outstanding at January 1, 2019 6,299,803 ​ $ 120.78 ​ ​ ​ ​ ​ Granted 2,081,047 ​ 124.87 ​ ​ ​ ​ ​ Exercised (191,508) ​ 51.53 ​ ​ ​ ​ ​ Forfeited/canceled (95,016) ​ 131.04 ​ ​ ​ ​ ​ Outstanding at September 30, 2019 8,094,326 ​ $ 123.35 6.5 ​ $ 8.4 Exercisable at September 30, 2019 3,915,462 ​ $ 119.40 5.4 ​ $ 8.2 Unvested at September 30, 2019 4,178,864 ​ $ 127.05 7.6 ​ $ 0.2 ​ The weighted average fair value of a stock option granted during each of the nine-month periods ended September 30, 2019 and September 30, 2018, was $39.63 and $45.02, respectively. These stock options have an aggregate grant date fair value of $82.5 million and $44.3 million, respectively. The total grant date fair value of stock options that vested during the nine-month periods ended September 30, 2019 and September 30, 2018 was $36.4 million and $33.9 million, respectively. Total share-based compensation expense relating to stock options is recorded as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, September 30, ​ 2019 2018 2019 2018 Cost of product sales ​ $ 0.3 $ 0.2 ​ $ 0.7 $ 0.7 Research and development ​ 0.9 ​ 0.9 ​ 2.7 ​ 2.8 Selling, general and administrative ​ 17.2 ​ 15.5 ​ 48.8 ​ 41.3 Share-based compensation expense before taxes ​ 18.4 ​ 16.6 ​ 52.2 ​ 44.8 Related income tax benefit ​ (4.2) ​ (3.8) ​ (11.8) ​ (10.3) Share-based compensation expense, net of taxes ​ $ 14.2 $ 12.8 ​ $ 40.4 $ 34.5 ​ As of September 30, 2019, unrecognized compensation expense relating to stock options was $108.4 million. Unvested outstanding stock options as of September 30, 2019 had a weighted average remaining vesting period of 2.6 years. Stock option exercise data is summarized below (dollars in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Number of options exercised ​ — ​ 4,857 ​ 191,508 ​ 287,760 Cash received ​ $ — ​ $ 0.6 ​ $ 9.9 ​ $ 15.5 Total intrinsic value of options exercised ​ $ — ​ $ 0.1 ​ $ 11.5 ​ $ 17.0 ​ Restricted Stock Units Each restricted stock unit entitles the recipient to one share of our common stock upon vesting. We measure the fair value of restricted stock units using the stock price on the date of grant. Share-based compensation expense for the restricted stock units is recorded ratably over their vesting period. A summary of the activity with respect to, and status of, restricted stock units during the nine-month period ended September 30, 2019 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted- Average Aggregate ​ Number of Average Remaining Intrinsic ​ ​ Restricted Grant Contractual Value ​ ​ Stock Units ​ Price Term (Years) ​ (in millions) Unvested at January 1, 2019 186,255 ​ $ 112.48 ​ Granted 222,614 ​ 113.03 ​ Vested (69,761) ​ 111.81 ​ Forfeited/canceled (18,445) ​ 118.24 ​ Unvested at September 30, 2019 320,663 ​ $ 112.68 9.2 ​ $ 25.6 ​ Total share-based compensation expense relating to restricted stock units is recorded as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Cost of product sales $ 0.3 ​ $ 0.1 $ 0.8 ​ $ 0.3 Research and development ​ 1.3 ​ 0.5 ​ 3.2 ​ 1.1 Selling, general and administrative ​ 2.2 ​ 1.8 ​ 5.8 ​ 3.9 Share-based compensation expense before taxes ​ 3.8 ​ 2.4 ​ 9.8 ​ 5.3 Related income tax benefit ​ (0.8) ​ (0.5) ​ (2.2) ​ (1.2) Share-based compensation expense, net of taxes ​ $ 3.0 ​ $ 1.9 ​ $ 7.6 ​ $ 4.1 ​ As of September 30, 2019, unrecognized compensation cost related to the grant of restricted stock units was $28.4 million. Unvested outstanding restricted stock units as of September 30, 2019 had a weighted average remaining vesting period of 2.1 years. Share Tracking Awards Plans 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. The aggregate STAP liability balance was $18.3 million and $72.2 million at September 30, 2019 and December 31, 2018, respectively, all of which was classified as a current liability on our consolidated balance sheets. 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, and the expected dividend yield. Prior to December 31, 2018, we used historical data to develop the expected term input for our STAP awards. As of December 31, 2018, we no longer believed historical exercise data formed a reasonable basis from which to determine the expected exercise behavior of outstanding STAPs given the prolonged volatility of the price of our common stock. As such, we began determining the expected term assumption as of December 31, 2018 using the weighted average midpoint of the remaining contractual term for outstanding awards and expect to continue to use this methodology until circumstances dictate otherwise. The fair value of the STAP awards is measured at the end of each financial reporting period because the awards are settled in cash. The table below includes the weighted-average assumptions used to measure the fair value of outstanding STAP awards: ​ ​ ​ ​ ​ ​ ​ ​ September 30, September 30, ​ 2019 2018 ​ Expected volatility 29.3 % 33.4 % Risk-free interest rate 1.6 % 2.5 % Expected term of awards (in years) 2.1 0.9 ​ Expected dividend yield — % — % ​ The closing price of our common stock was $79.75 and $127.88 on September 30, 2019 and September 30, 2018, respectively. The closing price of our common stock was $108.90 on December 31, 2018. A summary of the activity and status of STAP awards during the nine-month period ended September 30, 2019 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ Average Contractual Intrinsic ​ ​ Number of ​ Exercise Term ​ Value ​ ​ Awards ​ Price (in Years) ​ (in millions) Outstanding at January 1, 2019 2,867,979 ​ $ 107.85 ​ Granted — ​ — ​ Exercised (138,773) ​ 59.36 ​ Forfeited/canceled (80,182) ​ 159.91 ​ Outstanding at September 30, 2019 2,649,024 ​ $ 108.82 4.3 ​ $ 22.4 Exercisable at September 30, 2019 2,639,024 ​ $ 109.03 4.3 ​ $ 22.1 Unvested at September 30, 2019 10,000 ​ $ 52.57 3.2 ​ $ 0.3 ​ Share-based compensation expense (benefit) recognized in connection with STAP awards is as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Cost of product sales ​ $ 0.1 ​ $ 2.0 ​ $ (1.9) ​ $ (4.0) Research and development ​ 0.4 ​ 6.8 ​ (9.9) ​ (15.2) Selling, general and administrative ​ 0.9 ​ 23.4 ​ (35.2) ​ (60.9) Share-based compensation expense (benefit) before taxes ​ ​ 1.4 ​ ​ 32.2 ​ ​ (47.0) ​ ​ (80.1) Related income tax (benefit) expense ​ (0.2) ​ (7.4) ​ 10.7 ​ 18.3 Share-based compensation expense (benefit), net of taxes ​ $ 1.2 ​ $ 24.8 ​ $ (36.3) ​ $ (61.8) ​ Cash paid to settle STAP exercises during the nine-month periods ended September 30, 2019 and September 30, 2018 was $6.9 million and $71.5 million, respectively. Employee Stock Purchase Plan In June 2012, our shareholders approved the ESPP, which is 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 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.

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Common Share
Earnings Per Common Share	9. Earnings Per Common Share Basic earnings per common 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, adjusted for the potential dilutive effect of our outstanding stock options, as if such options were exercised. For the nine months ended September 30, 2019, we had a net loss, and as such, all outstanding stock options and restricted stock units were excluded from our calculation of diluted loss per share. The components of basic and diluted earnings (loss) per common share comprised the following (in millions, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ 132.4 ​ $ 106.5 ​ $ (157.1) ​ $ 523.9 Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average outstanding shares — basic ​ 43.9 ​ 43.6 ​ 43.8 ​ 43.5 Effect of dilutive securities (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options, restricted stock units and employee stock purchase plan ​ ​ 0.1 ​ ​ 0.4 ​ ​ — ​ ​ 0.5 Weighted average shares — diluted (2) ​ 44.0 ​ 44.0 ​ 43.8 ​ 44.0 Net income (loss) per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ $ 3.02 ​ $ 2.44 ​ $ (3.59) ​ $ 12.04 Diluted ​ $ 3.01 ​ $ 2.42 ​ $ (3.59) ​ $ 11.91 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options and restricted stock units excluded from calculation (2) ​ 8.0 ​ 4.5 ​ 7.1 ​ 4.6 (1) Calculated using the treasury stock method. (2) The common shares underlying certain stock options and restricted stock units have been excluded from the computation of diluted earnings per share because their impact would be anti-dilutive for the three-and nine-month periods ended September 30, 2019 and September 30, 2018.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Taxes
Income Taxes	10. Income Taxes Our effective income tax rate (ETR) for the nine months ended September 30, 2019 and 2018 was 33 percent and 21 percent, respectively. We recognized a loss before income taxes, and a corresponding income tax benefit, for the nine months ended September 30, 2019, as a result of the one-time $800.0 million payment to Arena in January 2019. As a result of this loss, our anticipated tax credits and foreign sales deduction, partially offset by non-deductible compensation expense, increased our tax benefit and resulting ETR for the nine months ended September 30, 2019 compared to the nine months ended September 30, 2018. Deferred tax assets increased by $172.4 million as of September 30, 2019 compared to December 31, 2018 primarily due to the amount of the Arena payment that will not be deductible for tax purposes in 2019. Our unrecognized tax benefits were $0.9 million for the nine months ended September 30, 2019 and September 30, 2018, and included $0.7 million of tax benefits that, if recognized, would impact our ETR. We record interest and penalties related to uncertain tax positions as a component of income tax expense. As of September 30, 2019, and 2018, we have not accrued any material interest expense related to uncertain tax positions. We are unaware of any material positions for which it is reasonably possible that the total amounts of unrecognized tax benefits will significantly increase or decrease within the next twelve months.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2019
Segment Information
Segment Information	11. 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 our overall level of available resources and determine how best to deploy these resources across functions, therapeutic areas, and research and development projects 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 Remodulin Tyvaso Orenitram Unituxin Adcirca Total Net product sales ​ $ 168.3 ​ $ 110.8 ​ $ 62.0 ​ $ 30.1 ​ $ 30.3 ​ $ 401.5 Cost of product sales ​ 5.5 ​ 6.9 ​ 3.5 ​ 4.1 ​ ​ 13.0 ​ 33.0 Gross profit ​ $ 162.8 ​ $ 103.9 ​ $ 58.5 ​ $ 26.0 ​ $ 17.3 ​ $ 368.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net product sales ​ $ 153.6 ​ $ 107.8 ​ $ 53.8 ​ $ 22.9 ​ $ 74.6 ​ $ 412.7 Cost of product sales ​ 4.4 ​ 6.9 ​ 3.9 ​ 4.2 ​ 32.5 ​ 51.9 Gross profit ​ $ 149.2 ​ $ 100.9 ​ $ 49.9 ​ $ 18.7 ​ $ 42.1 ​ $ 360.8 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 Remodulin Tyvaso Orenitram Unituxin Adcirca Total Net product sales ​ $ 479.6 ​ $ 324.2 ​ $ 174.4 ​ $ 80.1 ​ $ 79.4 ​ $ 1,137.7 Cost of product sales ​ 16.1 ​ 14.8 ​ 12.3 ​ 11.4 ​ ​ 34.2 ​ 88.8 Gross profit ​ $ 463.5 ​ $ 309.4 ​ $ 162.1 ​ $ 68.7 ​ $ 45.2 ​ $ 1,048.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net product sales ​ $ 439.9 ​ $ 308.3 ​ $ 155.5 ​ $ 60.7 ​ $ 282.0 ​ $ 1,246.4 Cost of product sales ​ 10.8 ​ 14.3 ​ 9.9 ​ 9.9 ​ ​ 121.9 ​ 166.8 Gross profit ​ $ 429.1 ​ $ 294.0 ​ $ 145.6 ​ $ 50.8 ​ $ 160.1 ​ $ 1,079.6 ​ 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 United States ​ $ 359.4 ​ $ 389.0 ​ $ 1,028.4 ​ $ 1,177.1 Rest-of-World (1) ​ 42.1 ​ 23.7 ​ 109.3 ​ 69.3 Total ​ $ 401.5 ​ $ 412.7 ​ $ 1,137.7 ​ $ 1,246.4 (1) Primarily Europe. We recorded revenue from two specialty pharmaceutical distributors in the United States. Total revenue from these two specialty pharmaceutical distributors as a percentage of total revenues are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Distributor 1 53 % 52 % 55 % 50 % Distributor 2 21 % 18 % 21 % 17 % ​

Litigation

Litigation	9 Months Ended
	Sep. 30, 2019
Litigation
Litigation	12. Litigation On April 16, 2019, Sandoz Inc. (Sandoz) and its commercialization collaborator, RareGen, LLC, filed a complaint in the U.S. District Court for the District of New Jersey against us and Smiths Medical ASD, Inc. (Smiths Medical), alleging that we and Smiths Medical engaged in anticompetitive conduct in connection with plaintiffs’ efforts to launch their generic version of Remodulin. In particular, the complaint alleges that we and Smiths Medical unlawfully impeded competition by entering into an agreement to produce CADD MS ® 3 cartridges specifically for the delivery of subcutaneous Remodulin, without making these cartridges available for the delivery of Sandoz’s generic version of Remodulin. The parties have completed expedited discovery in anticipation of a motion filed by the plaintiffs on October 4, 2019, seeking preliminary injunctive relief. We and Smiths Medical have filed a motion to dismiss the complaint, and we filed our opposition to plaintiffs’ motion for a preliminary injunction on October 25, 2019. We believe plaintiffs’ claims to be meritless and intend to vigorously defend the litigation. However, due to the uncertainty inherent in any litigation, we cannot guarantee that an adverse outcome will not result. Any litigation of this nature could involve substantial cost, and an adverse outcome could result in substantial monetary damages and/or injunctive relief adverse to our business. We currently are not able to reasonably estimate a range of potential losses due to the early stage of the litigation.

Arena License Agreement

Arena License Agreement	9 Months Ended
	Sep. 30, 2019
Arena License Agreement
Arena License Agreement	13. Arena License Agreement On November 15, 2018, we entered into an exclusive license agreement with Arena related to ralinepag, a next-generation, oral, selective and potent prostacyclin receptor agonist being developed for the treatment of PAH. On January 24, 2019, in connection with the closing of the transactions contemplated by the license agreement: (1) Arena granted to us perpetual, irrevocable and exclusive rights throughout the universe to develop, manufacture and commercialize ralinepag; (2) Arena transferred to us certain other assets related to ralinepag, including, among others, related domain names and trademarks, permits, certain contracts, inventory, regulatory documentation, Investigational New Drug (IND) Application No. 109021 (related to ralinepag) and non-clinical, pre-clinical and clinical trial data; (3) we assumed certain limited liabilities from Arena, including, among others, all obligations arising after the closing under the assumed contracts and the IND described above; and (4) we paid Arena an upfront payment of $800.0 million, which was expensed as acquired in-process research and development and included within research and development expenses on our consolidated statements of operations in the first quarter of 2019. We will also pay Arena: (1) a one-time payment of $250.0 million for the first, if any, marketing approval we receive in the United States for an inhaled version of ralinepag to treat PAH; (2) a one-time payment of $150.0 million for the first, if any, marketing approval we receive in any of Japan, France, Italy, the United Kingdom, Spain or Germany for an oral version of ralinepag to treat any indication; and (3) low double-digit, tiered royalties on net sales of any pharmaceutical product containing ralinepag as an active ingredient, subject to certain adjustments for third party license payments.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2019
Basis of Presentation
Recently Issued Accounting Standards	Recently Issued Accounting Standards Accounting Standards Adopted During the Period In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Leases (Topic 842)—Targeted Improvements Upon adoption of this standard, we recognized a right-of-use asset of $8.2 million, and a corresponding lease liability of the same amount, related to our operating leases as of January 1, 2019. In addition, we recognized a cumulative-effect adjustment for the de-recognition of our build-to-suit leases as these leases no longer qualify for build-to-suit accounting and have instead been recognized as operating leases under ASC 842. The adjustment resulted in a decrease to retained earnings of $5.1 million, which is net of a tax benefit. At adoption, our weighted-average remaining lease term was 3.0 years and our weighted-average discount rate was 4.9%. Supplemental balance sheet information related to operating leases was as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial Statement Line Item on our September 30, January 1, Operating Leases ​ Consolidated Balance Sheets ​ 2019 ​ 2019 Right-of-use assets Other non-current assets ​ $ 4.7 ​ $ 8.2 Current lease liabilities Other current liabilities ​ $ 1.9 ​ $ 4.1 Non-current lease liabilities Other non-current liabilities ​ 2.8 ​ 4.1 Total operating lease liabilities ​ $ 4.7 ​ $ 8.2 ​ We recorded $1.2 million and $3.9 million in operating lease expense for the three and nine months ended September 30, 2019 and recorded $1.0 million and $3.2 million in operating lease expense for the three and nine months ended September 30, 2018. The amounts recorded in operating lease expense include short-term leases and variable lease costs, which are immaterial. In connection with completion of construction in the third quarter of 2019 of a building we own, we leased part of the space in the building to another entity as part of a broader collaboration arrangement. The lease is accounted for as a sales-type lease. Upon lease commencement in the third quarter of 2019, we reclassified $23.1 million of property, plant and equipment, net to other non-current assets on our consolidated balance sheets. The collaboration arrangement activity was immaterial for the period ended September 30, 2019. In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, to eliminate or modify certain disclosure rules that are redundant, outdated, or duplicative of U.S. GAAP or other regulatory requirements. Among other changes, the amendments eliminated the annual requirement to disclose the high and low trading prices of our common stock. In addition, the amendments expanded the disclosure requirements related to the analysis of shareholders’ equity for interim financial statements. An analysis of the changes in each caption of shareholders’ equity presented in the balance sheet must be provided in a note or separate statement, and we have provided this disclosure in a separate statement (Consolidated Statements of Stockholders’ Equity) beginning in the first quarter of 2019. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other: Simplifying the Test for Goodwill Impairment In August 2018, the FASB issued ASU No. 2018-14, Compensation-Retirement Benefits-Defined Benefit Plans-General (Topic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans

Basis of Presentation (Tables)

Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2019
Basis of Presentation
Schedule of Supplemental balance sheet information related to operating leases	Supplemental balance sheet information related to operating leases was as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financial Statement Line Item on our September 30, January 1, Operating Leases ​ Consolidated Balance Sheets ​ 2019 ​ 2019 Right-of-use assets Other non-current assets ​ $ 4.7 ​ $ 8.2 Current lease liabilities Other current liabilities ​ $ 1.9 ​ $ 4.1 Non-current lease liabilities Other non-current liabilities ​ 2.8 ​ 4.1 Total operating lease liabilities ​ $ 4.7 ​ $ 8.2

Investments (Tables)

Investments (Tables) - Available-for-Sale Debt Securities	9 Months Ended
	Sep. 30, 2019
Investments
Schedule of available-for-sale debt securities	Available-for-sale debt securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income in stockholders’ equity, until realized. Available-for-sale debt securities consisted of the following (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair As of September 30, 2019 Cost ​ Gains Losses Value U.S. government and agency securities ​ $ 1,287.9 ​ $ 3.2 ​ $ (0.5) ​ $ 1,290.6 Corporate debt securities ​ ​ 223.6 ​ ​ 1.8 ​ ​ (0.1) ​ ​ 225.3 Total ​ $ 1,511.5 ​ $ 5.0 ​ $ (0.6) ​ $ 1,515.9 Reported under the following captions on our consolidated balance sheet: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 785.5 Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 730.4 Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,515.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair As of December 31, 2018 Cost ​ Gains Losses Value U.S. government and agency securities ​ $ 1,077.4 ​ $ 0.7 ​ $ (3.9) ​ $ 1,074.2 Corporate debt securities ​ ​ 72.3 ​ ​ — ​ ​ (0.3) ​ ​ 72.0 Total ​ $ 1,149.7 ​ $ 0.7 ​ $ (4.2) ​ $ 1,146.2 Reported under the following captions on our consolidated balance sheet: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 705.8 Non-current marketable investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 440.4 Total ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,146.2
Summary of the contractual maturities	The following table summarizes the contractual maturities of available-for-sale marketable investments (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ Amortized Fair ​ Cost Value Due within one year ​ $ 784.7 ​ $ 785.5 Due in one to three years ​ ​ 726.8 ​ ​ 730.4 Total ​ $ 1,511.5 ​ $ 1,515.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ Amortized Fair ​ Cost Value Due within one year ​ $ 708.2 ​ $ 705.8 Due in one to three years ​ 441.5 ​ ​ 440.4 Total ​ $ 1,149.7 ​ $ 1,146.2

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Measurements
Schedule of assets and liabilities subject to fair value measurements	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ Level 1 Level 2 Level 3 Balance Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 253.4 ​ $ — ​ $ — ​ $ 253.4 Time deposits (2) ​ ​ — ​ ​ 86.9 ​ ​ — ​ ​ 86.9 U.S. government and agency securities (3) ​ ​ — ​ ​ 1,290.6 ​ ​ — ​ ​ 1,290.6 Corporate debt securities (3) ​ — ​ 225.3 ​ — ​ 225.3 Equity securities (4) ​ ​ 64.8 ​ ​ — ​ ​ — ​ ​ 64.8 Total assets ​ $ 318.2 ​ $ 1,602.8 ​ $ — ​ $ 1,921.0 Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (5) ​ — ​ — ​ 13.4 ​ 13.4 Total liabilities ​ $ — ​ $ — ​ $ 13.4 ​ $ 13.4 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ Level 1 Level 2 Level 3 Balance Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 247.6 ​ $ — ​ $ — ​ $ 247.6 Time deposits (2) ​ ​ — ​ ​ 35.9 ​ ​ — ​ ​ 35.9 U.S. government and agency securities (3) ​ ​ — ​ ​ 1,074.2 ​ ​ — ​ ​ 1,074.2 Corporate debt securities (3) ​ — ​ 75.7 ​ — ​ 75.7 Equity securities (4) ​ ​ 3.5 ​ ​ — ​ ​ — ​ ​ 3.5 Total assets ​ $ 251.1 ​ $ 1,185.8 ​ $ — ​ $ 1,436.9 Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (5) ​ — ​ — ​ 13.4 ​ 13.4 Total liabilities ​ $ — ​ $ — ​ $ 13.4 ​ $ 13.4 (1) Included in cash and cash equivalents on our consolidated balance sheets. (2) Included in cash equivalents and current and non-current marketable investments on our 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. (3) Included in cash equivalents and current and non-current marketable investments on our consolidated balance sheets. Refer to Note 3 —Investments—Available-for-Sale Debt Securities for further information. The fair value of these securities is principally measured or corroborated by trade data for identical securities for which related trading activity is not sufficiently frequent to be considered a Level 1 input or comparable securities that are more actively traded. (4) Included in current marketable investments on our consolidated balance sheets. The fair value of these securities is based on quoted market prices for identical instruments in active markets. During the three and nine months ended September 30, 2019, we recognized $13.0 million of net unrealized losses and $19.5 million of net unrealized gains, respectively, on these securities and recorded these losses and gains on our consolidated statements of operations within other (expense) income, net. Refer to Note 3 —Investments—Investments in Equity Securities with Readily Determinable Fair Values. (5) Included in non-current liabilities on our consolidated balance sheets. The fair value of contingent consideration has been estimated using probability-weighted discounted cash flow models (DCFs). The DCFs incorporate 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. The change in the fair value of contingent consideration for the three and nine months ended September 30, 2019 was not material.

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2019
Inventories
Schedule of inventories, net of reserves	Inventories are stated at the lower of cost (first-in, first-out method) or net realizable value and consist of the following, net of reserves (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2019 ​ 2018 Raw materials ​ $ 19.3 ​ $ 24.3 Work-in-progress ​ 29.8 ​ 28.0 Finished goods ​ 45.0 ​ 48.7 Total inventories ​ $ 94.1 ​ $ 101.0

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill and Other Intangible Assets
Schedule of goodwill and other intangible assets	Goodwill and other intangible assets comprise the following (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2019 ​ As of December 31, 2018 ​ ​ ​ Accumulated ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Gross ​ Amortization ​ Net ​ Gross ​ Amortization ​ Net Goodwill ​ $ 28.0 ​ $ — ​ $ 28.0 ​ $ 31.5 ​ $ — ​ $ 31.5 Other intangible assets: ​ ​ ​ ​ ​ ​ Technology, patents and trade names ​ 6.7 ​ (5.2) ​ 1.5 ​ 6.7 ​ (5.1) ​ 1.6 In-process research and development ​ 128.9 ​ — ​ 128.9 ​ 137.7 ​ — ​ 137.7 Total ​ $ 163.6 ​ $ (5.2) ​ $ 158.4 ​ $ 175.9 ​ $ (5.1) ​ $ 170.8

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Stock Options
Share-Based Compensation
Schedule of components of share-based compensation expense (benefit) recognized	The following table reflects the components of share-based compensation expense (benefit) recognized in our consolidated statements of operations (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Stock options ​ $ 18.4 ​ $ 16.6 ​ $ 52.2 ​ $ 44.8 Restricted stock units ​ 3.8 ​ 2.4 ​ 9.8 ​ 5.3 STAP awards ​ 1.4 ​ 32.2 ​ (47.0) ​ (80.1) Employee stock purchase plan ​ 0.3 ​ 0.2 ​ 0.9 ​ 0.8 Total share-based compensation expense (benefit) before tax ​ $ 23.9 ​ $ 51.4 ​ $ 15.9 ​ $ (29.2) ​
Summary of weighted-average assumptions to measure the fair value of stock options	​ ​ ​ ​ ​ ​ ​ ​ September 30, September 30, ​ ​ 2019 2018 ​ Expected volatility 33.8 % 36.2 % Risk-free interest rate 2.4 % 2.7 % Expected term of awards (in years) 5.8 ​ 6.3 ​ Expected dividend yield 0.0 % 0.0 % ​
Schedule of activity and status of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted- Average Aggregate ​ ​ ​ Average Remaining ​ Intrinsic ​ ​ Number of ​ Exercise ​ Contractual ​ Value ​ Options Price Term (Years) (in millions) Outstanding at January 1, 2019 6,299,803 ​ $ 120.78 ​ ​ ​ ​ ​ Granted 2,081,047 ​ 124.87 ​ ​ ​ ​ ​ Exercised (191,508) ​ 51.53 ​ ​ ​ ​ ​ Forfeited/canceled (95,016) ​ 131.04 ​ ​ ​ ​ ​ Outstanding at September 30, 2019 8,094,326 ​ $ 123.35 6.5 ​ $ 8.4 Exercisable at September 30, 2019 3,915,462 ​ $ 119.40 5.4 ​ $ 8.2 Unvested at September 30, 2019 4,178,864 ​ $ 127.05 7.6 ​ $ 0.2 ​
Schedule of share-based compensation expense (benefit) recognized	Total share-based compensation expense relating to stock options is recorded as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, September 30, ​ 2019 2018 2019 2018 Cost of product sales ​ $ 0.3 $ 0.2 ​ $ 0.7 $ 0.7 Research and development ​ 0.9 ​ 0.9 ​ 2.7 ​ 2.8 Selling, general and administrative ​ 17.2 ​ 15.5 ​ 48.8 ​ 41.3 Share-based compensation expense before taxes ​ 18.4 ​ 16.6 ​ 52.2 ​ 44.8 Related income tax benefit ​ (4.2) ​ (3.8) ​ (11.8) ​ (10.3) Share-based compensation expense, net of taxes ​ $ 14.2 $ 12.8 ​ $ 40.4 $ 34.5 ​
Summary of stock option exercise data	Stock option exercise data is summarized below (dollars in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Number of options exercised ​ — ​ 4,857 ​ 191,508 ​ 287,760 Cash received ​ $ — ​ $ 0.6 ​ $ 9.9 ​ $ 15.5 Total intrinsic value of options exercised ​ $ — ​ $ 0.1 ​ $ 11.5 ​ $ 17.0 ​
Restricted Stock Units
Share-Based Compensation
Schedule of restricted stock units activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Weighted- Average Aggregate ​ Number of Average Remaining Intrinsic ​ ​ Restricted Grant Contractual Value ​ ​ Stock Units ​ Price Term (Years) ​ (in millions) Unvested at January 1, 2019 186,255 ​ $ 112.48 ​ Granted 222,614 ​ 113.03 ​ Vested (69,761) ​ 111.81 ​ Forfeited/canceled (18,445) ​ 118.24 ​ Unvested at September 30, 2019 320,663 ​ $ 112.68 9.2 ​ $ 25.6 ​
Schedule of share-based compensation expense (benefit) recognized	Total share-based compensation expense relating to restricted stock units is recorded as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Cost of product sales $ 0.3 ​ $ 0.1 $ 0.8 ​ $ 0.3 Research and development ​ 1.3 ​ 0.5 ​ 3.2 ​ 1.1 Selling, general and administrative ​ 2.2 ​ 1.8 ​ 5.8 ​ 3.9 Share-based compensation expense before taxes ​ 3.8 ​ 2.4 ​ 9.8 ​ 5.3 Related income tax benefit ​ (0.8) ​ (0.5) ​ (2.2) ​ (1.2) Share-based compensation expense, net of taxes ​ $ 3.0 ​ $ 1.9 ​ $ 7.6 ​ $ 4.1 ​
STAP awards
Share-Based Compensation
Schedule of share-based compensation expense (benefit) recognized	Share-based compensation expense (benefit) recognized in connection with STAP awards is as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Cost of product sales ​ $ 0.1 ​ $ 2.0 ​ $ (1.9) ​ $ (4.0) Research and development ​ 0.4 ​ 6.8 ​ (9.9) ​ (15.2) Selling, general and administrative ​ 0.9 ​ 23.4 ​ (35.2) ​ (60.9) Share-based compensation expense (benefit) before taxes ​ ​ 1.4 ​ ​ 32.2 ​ ​ (47.0) ​ ​ (80.1) Related income tax (benefit) expense ​ (0.2) ​ (7.4) ​ 10.7 ​ 18.3 Share-based compensation expense (benefit), net of taxes ​ $ 1.2 ​ $ 24.8 ​ $ (36.3) ​ $ (61.8) ​
Schedule of weighted-average assumptions to measure the fair value of outstanding STAP awards	​ ​ ​ ​ ​ ​ ​ ​ September 30, September 30, ​ 2019 2018 ​ Expected volatility 29.3 % 33.4 % Risk-free interest rate 1.6 % 2.5 % Expected term of awards (in years) 2.1 0.9 ​ Expected dividend yield — % — % ​
Summary of the activity and status of STAP awards	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Weighted Remaining Aggregate ​ ​ ​ Average Contractual Intrinsic ​ ​ Number of ​ Exercise Term ​ Value ​ ​ Awards ​ Price (in Years) ​ (in millions) Outstanding at January 1, 2019 2,867,979 ​ $ 107.85 ​ Granted — ​ — ​ Exercised (138,773) ​ 59.36 ​ Forfeited/canceled (80,182) ​ 159.91 ​ Outstanding at September 30, 2019 2,649,024 ​ $ 108.82 4.3 ​ $ 22.4 Exercisable at September 30, 2019 2,639,024 ​ $ 109.03 4.3 ​ $ 22.1 Unvested at September 30, 2019 10,000 ​ $ 52.57 3.2 ​ $ 0.3 ​

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Common Share
Schedule of components of basic and diluted earnings (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2019 2018 2019 2018 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ 132.4 ​ $ 106.5 ​ $ (157.1) ​ $ 523.9 Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average outstanding shares — basic ​ 43.9 ​ 43.6 ​ 43.8 ​ 43.5 Effect of dilutive securities (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options, restricted stock units and employee stock purchase plan ​ ​ 0.1 ​ ​ 0.4 ​ ​ — ​ ​ 0.5 Weighted average shares — diluted (2) ​ 44.0 ​ 44.0 ​ 43.8 ​ 44.0 Net income (loss) per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ $ 3.02 ​ $ 2.44 ​ $ (3.59) ​ $ 12.04 Diluted ​ $ 3.01 ​ $ 2.42 ​ $ (3.59) ​ $ 11.91 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options and restricted stock units excluded from calculation (2) ​ 8.0 ​ 4.5 ​ 7.1 ​ 4.6 (1) Calculated using the treasury stock method. (2) The common shares underlying certain stock options and restricted stock units have been excluded from the computation of diluted earnings per share because their impact would be anti-dilutive for the three-and nine-month periods ended September 30, 2019 and September 30, 2018.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Information
Schedule of net product sales, cost of product sales and gross profit for each commercial products	Net product sales, cost of product sales and gross profit for each of our commercial products were as follows (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 Remodulin Tyvaso Orenitram Unituxin Adcirca Total Net product sales ​ $ 168.3 ​ $ 110.8 ​ $ 62.0 ​ $ 30.1 ​ $ 30.3 ​ $ 401.5 Cost of product sales ​ 5.5 ​ 6.9 ​ 3.5 ​ 4.1 ​ ​ 13.0 ​ 33.0 Gross profit ​ $ 162.8 ​ $ 103.9 ​ $ 58.5 ​ $ 26.0 ​ $ 17.3 ​ $ 368.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net product sales ​ $ 153.6 ​ $ 107.8 ​ $ 53.8 ​ $ 22.9 ​ $ 74.6 ​ $ 412.7 Cost of product sales ​ 4.4 ​ 6.9 ​ 3.9 ​ 4.2 ​ 32.5 ​ 51.9 Gross profit ​ $ 149.2 ​ $ 100.9 ​ $ 49.9 ​ $ 18.7 ​ $ 42.1 ​ $ 360.8 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 Remodulin Tyvaso Orenitram Unituxin Adcirca Total Net product sales ​ $ 479.6 ​ $ 324.2 ​ $ 174.4 ​ $ 80.1 ​ $ 79.4 ​ $ 1,137.7 Cost of product sales ​ 16.1 ​ 14.8 ​ 12.3 ​ 11.4 ​ ​ 34.2 ​ 88.8 Gross profit ​ $ 463.5 ​ $ 309.4 ​ $ 162.1 ​ $ 68.7 ​ $ 45.2 ​ $ 1,048.9 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net product sales ​ $ 439.9 ​ $ 308.3 ​ $ 155.5 ​ $ 60.7 ​ $ 282.0 ​ $ 1,246.4 Cost of product sales ​ 10.8 ​ 14.3 ​ 9.9 ​ 9.9 ​ ​ 121.9 ​ 166.8 Gross profit ​ $ 429.1 ​ $ 294.0 ​ $ 145.6 ​ $ 50.8 ​ $ 160.1 ​ $ 1,079.6
Schedule of net revenues from external customers by geographic area	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): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 United States ​ $ 359.4 ​ $ 389.0 ​ $ 1,028.4 ​ $ 1,177.1 Rest-of-World (1) ​ 42.1 ​ 23.7 ​ 109.3 ​ 69.3 Total ​ $ 401.5 ​ $ 412.7 ​ $ 1,137.7 ​ $ 1,246.4 (1) Primarily Europe.
Schedule of revenue from two specialty pharmaceutical distributors in the United States as a percentage of total revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2019 2018 2019 2018 Distributor 1 53 % 52 % 55 % 50 % Distributor 2 21 % 18 % 21 % 17 %

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Millions	Jan. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases
Decrease to retained earnings				$ (5.1)
Right-of-use assets	$ 8.2	$ 4.7		$ 4.7
Other non-current assets		us-gaap:OtherAssetsNoncurrent		us-gaap:OtherAssetsNoncurrent
Current lease liabilities	4.1	$ 1.9		$ 1.9
Other current liabilities		us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Non-current lease liabilities	4.1	$ 2.8		$ 2.8
Other non-current liabilities		us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Total operating lease liabilities	8.2	$ 4.7		$ 4.7
Operating lease expense		1.2	$ 1	$ 3.9	$ 3.2
Broader collaboration arrangement
Leases
Reclassification from Property, plant and equipment to other noncurrent assets		$ 23.1
ASU 2016-02
Leases
Decrease to retained earnings	$ (5.1)
Weighted-average remaining lease term	3 years
Weighted-average discount rate	4.90%

Investments - Available-for-Sal

Investments - Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Marketable investments classified as available-for-sale securities:
Amortized Cost	$ 1,511.5	$ 1,149.7
Gross Unrealized Gains	5	0.7
Gross Unrealized Losses	(0.6)	(4.2)
Fair Value	1,515.9	1,146.2
U.S. government and agency securities
Marketable investments classified as available-for-sale securities:
Amortized Cost	1,287.9	1,077.4
Gross Unrealized Gains	3.2	0.7
Gross Unrealized Losses	(0.5)	(3.9)
Fair Value	1,290.6	1,074.2
Corporate debt securities
Marketable investments classified as available-for-sale securities:
Amortized Cost	223.6	72.3
Gross Unrealized Gains	1.8	0
Gross Unrealized Losses	(0.1)	(0.3)
Fair Value	$ 225.3	$ 72

Investments - Current and Non-c

Investments - Current and Non-current of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Reported under the following captions on our consolidated balance sheet:
Total	$ 1,515.9	$ 1,146.2
Current marketable investments
Reported under the following captions on our consolidated balance sheet:
Total	785.5	705.8
Non-current marketable investments
Reported under the following captions on our consolidated balance sheet:
Total	$ 730.4	$ 440.4

Investments - Contractual Matur

Investments - Contractual Maturities of Available-for-Sale Marketable Investments (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 784.7	$ 708.2
Due in one to three years	726.8	441.5
Total	1,511.5	1,149.7
Fair Value
Due within one year	785.5	705.8
Due in one to three years	730.4	440.4
Total	$ 1,515.9	$ 1,146.2

Investments - Additional Inform

Investments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Apr. 30, 2017
Investments in Privately-Held Companies and Investments in Equity Securities with Readily Determinable Fair Values
Impairment charges			$ 12.4		$ 12.4
Goodwill on deconsolidation	$ 3.5
Privately-held Companies
Investments in Privately-Held Companies and Investments in Equity Securities with Readily Determinable Fair Values
Investments	101.7			$ 101.7
Upward price changes of investments	0			0
Impairment charges					$ 12.4
Privately-held Companies | Variable Interest Entity
Investments in Privately-Held Companies and Investments in Equity Securities with Readily Determinable Fair Values
Minority equity investment in a privately-held company							$ 7.5
Impairment charge on research and development		$ 8.8
Goodwill on deconsolidation	3.5
Temporary equity derecognized		$ 8.4
Net loss on deconsolidating	(2)
Equity securities
Investments in Privately-Held Companies and Investments in Equity Securities with Readily Determinable Fair Values
Investments in equity securities with readily determinable fair value	$ 64.8			$ 64.8		$ 3.5

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring fair value measurements - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Equity securities | Other income (expense), net
Liabilities
Net unrealized losses on securities	$ 13
Net unrealized gains on securities		$ 19.5
Level 1
Assets
Total assets	318.2	318.2	$ 251.1
Level 1 | Money market funds
Assets
Total assets	253.4	253.4	247.6
Level 1 | Equity securities
Assets
Total assets	64.8	64.8	3.5
Level 2
Assets
Total assets	1,602.8	1,602.8	1,185.8
Level 2 | Time deposits
Assets
Total assets	86.9	86.9	35.9
Level 2 | U.S. government and agency securities
Assets
Total assets	1,290.6	1,290.6	1,074.2
Level 2 | Corporate debt securities
Assets
Total assets	225.3	225.3	75.7
Level 3
Liabilities
Contingent consideration	13.4	13.4	13.4
Total liabilities	13.4	13.4	13.4
Balance
Assets
Total assets	1,921	1,921	1,436.9
Liabilities
Contingent consideration	13.4	13.4	13.4
Total liabilities	13.4	13.4	13.4
Balance | Money market funds
Assets
Total assets	253.4	253.4	247.6
Balance | Time deposits
Assets
Total assets	86.9	86.9	35.9
Balance | U.S. government and agency securities
Assets
Total assets	1,290.6	1,290.6	1,074.2
Balance | Corporate debt securities
Assets
Total assets	225.3	225.3	75.7
Balance | Equity securities
Assets
Total assets	$ 64.8	$ 64.8	$ 3.5

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Inventories
Raw materials	$ 19.3	$ 24.3
Work-in-progress	29.8	28
Finished goods	45	48.7
Total inventories	$ 94.1	$ 101

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Goodwill and Other Intangible Assets
Goodwill, Gross	$ 28		$ 28	$ 31.5
Goodwill, Net	28		28	31.5
Total Goodwill and other intangible assets, Gross	163.6		163.6	175.9
Other intangible assets, Accumulated Amortization	(5.2)		(5.2)	(5.1)
Total goodwill and other intangible assets, Net	158.4		158.4	170.8
Impairment charges			8.8
Goodwill wrote off	3.5
Technology, patents and trade names
Goodwill and Other Intangible Assets
Other intangible assets, Gross	6.7		6.7	6.7
Other intangible assets, Accumulated Amortization	(5.2)		(5.2)	(5.1)
Other intangible assets, Net	1.5		1.5	1.6
In-process research and development
Goodwill and Other Intangible Assets
Other intangible assets, Gross	128.9		128.9	137.7
Other intangible assets, Accumulated Amortization				0
Other intangible assets, Net	$ 128.9		$ 128.9	$ 137.7
Impairment charges		$ 8.8

Debt (Details)

Debt (Details) - USD ($) $ in Millions	Jan. 24, 2019	Jun. 30, 2019	Jan. 31, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 27, 2018
Debt
Line of credit (current)					$ 250		$ 250
Debt issuance costs							0.7	$ 13.2
Arena Pharmaceuticals, Inc.
Debt
Upfront payment	$ 800		$ 800
Credit Agreement
Debt
Borrowing	800
Period of extension in maturity		1 year			1 year
Debt aggregate principal value									$ 250
Interest expense					$ 11.7	$ 4.1	34.2	9.6
Upfront payment	$ 800
Outstanding Balance					$ 1,000		1,000
Line of credit repaid during the period							$ 50
Debt issuance costs				$ 13.2
Debt issuance costs capitalized				12.6
First unsecured revolving credit facility
Debt
Borrowing						1,000		1,000
Second unsecured revolving credit facility
Debt
Borrowing						$ 500		$ 500
Increase in borrowing capacity				$ 300

Share-Based Compensation - Gene

Share-Based Compensation - General (Details)	1 Months Ended	9 Months Ended
	Feb. 28, 2019shares	Sep. 30, 2019itemshares
Share-Based Compensation
Number of equity incentive plans | item		2
2015 Plan
Share-Based Compensation
Maximum number of shares authorized to be issued		9,500,000
Additional number of shares authorized to be issued		450,000
2019 Inducement Plan | Newly-hired employees
Share-Based Compensation
Number of equity incentive plans		1
Granted (in shares)	99,000
Amended and Restated Equity Incentive Plan (The 1999 Plan)
Share-Based Compensation
Granted (in shares)		0

Share-Based Compensation - Allo

Share-Based Compensation - Allocation of Compensation Expense (Benefit) by Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-Based Compensation
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
Stock Options
Share-Based Compensation
Share-based compensation expense (benefit) before tax	18.4	16.6	52.2	44.8
Restricted Stock Units
Share-Based Compensation
Share-based compensation expense (benefit) before tax	3.8	2.4	9.8	5.3
STAP awards
Share-Based Compensation
Share-based compensation expense (benefit) before tax	1.4	32.2	(47)	(80.1)
Employee Stock Purchase Plan
Share-Based Compensation
Share-based compensation expense (benefit) before tax	$ 0.3	$ 0.2	$ 0.9	$ 0.8

Share-Based Compensation - Assu

Share-Based Compensation - Assumptions For Stock Options (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-Based Compensation
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
Stock Options
Share-Based Compensation
Granted (in shares)			2,081,047
Total grant date fair value of employee stock options that vested			$ 36.4	33.9
Share-based compensation expense (benefit) before tax	$ 18.4	$ 16.6	$ 52.2	$ 44.8
Method and assumptions on valuation of stock options
Expected volatility (as a percent)			33.80%	36.20%
Risk-free interest rate (as a percent)			2.40%	2.70%
Expected term of awards (in years)			5 years 9 months 18 days	6 years 3 months 18 days
Expected dividend yield (as a percent)			0.00%	0.00%

Share-Based Compensation - Stoc

Share-Based Compensation - Stock and Status (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Options
Outstanding at beginning of period (in shares)		6,299,803
Granted (in shares)		2,081,047
Exercised (in shares)	(4,857)	(191,508)	(287,760)
Forfeited/canceled (in shares)		(95,016)
Outstanding at the end of period (in shares)		8,094,326
Exercisable at the end of period (in shares)		3,915,462
Unvested at the end of period (in shares)		4,178,864
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)		$ 120.78
Granted (in dollars per share)		124.87
Exercised (in dollars per share)		51.53
Forfeited (in dollars per share)		131.04
Outstanding at the end of period (in dollars per share)		123.35
Exercisable at the end of period (in dollars per share)		119.40
Unvested at the end of period (in dollars per share)		$ 127.05
Weighted Average Remaining Contractual Term (in Years)
Outstanding at the end of period (in Years)		6 years 6 months
Exercisable at the end of period (in Years)		5 years 4 months 24 days
Unvested at the end of period (in Years)		7 years 7 months 6 days
Outstanding at the end of period)		$ 8.4
Exercisable at the end of period		8.2
Unvested at the end of period		$ 0.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Aggregate Intrinsic Value Disclosures [Abstract]
Weighted average grant date fair value of stock options (in dollars per share)		$ 39.63	$ 45.02
Aggregate grant date fair value		$ 82.5	$ 44.3
Total grant date fair value of employee stock options that vested		$ 36.4	$ 33.9

Share-Based Compensation - Shar

Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	18.4	16.6	52.2	44.8
Related income tax (benefit) expense	(4.2)	(3.8)	(11.8)	(10.3)
Share-based compensation expense (benefit), net of taxes	14.2	12.8	40.4	34.5
Unrecognized compensation cost	108.4		$ 108.4
Recognition of share-based compensation expense (in years)			2 years 7 months 6 days
Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	3.8	2.4	$ 9.8	5.3
Related income tax (benefit) expense	(0.8)	(0.5)	(2.2)	(1.2)
Share-based compensation expense (benefit), net of taxes	3	1.9	7.6	4.1
Unrecognized compensation cost	28.4		$ 28.4
Recognition of share-based compensation expense (in years)			2 years 1 month 6 days
Cost of product sales | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.3	0.2	$ 0.7	0.7
Cost of product sales | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.3	0.1	0.8	0.3
Research and development | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.9	0.9	2.7	2.8
Research and development | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	1.3	0.5	3.2	1.1
Selling, general and administrative | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	17.2	15.5	48.8	41.3
Selling, general and administrative | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 2.2	$ 1.8	$ 5.8	$ 3.9

Share-Based Compensation - St_2

Share-Based Compensation - Stock Options Exercise Data (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Summary of stock option exercise data
Cash received from options exercised		$ 9.9	$ 15.5
Stock Options
Summary of stock option exercise data
Number of options exercised (in shares)	4,857	191,508	287,760
Cash received from options exercised	$ 0.6	$ 9.9	$ 15.5
Total intrinsic value of options exercised	$ 0.1	$ 11.5	$ 17

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Options Activity and Status (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)item$ / sharesshares	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)item$ / sharesshares	Sep. 30, 2018USD ($)
Aggregate Intrinsic Value
Share-based compensation expense (benefit) before tax | $	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
Restricted Stock Units
Share-Based Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Entitled To Receive For Each Unit Upon Vesting | item	1		1
Number of Restricted Stock Units
Unvested at beginning of period (in shares) | shares			186,255
Granted (in shares) | shares			222,614
Vested (in shares) | shares			(69,761)
Forfeited/cancelled (in shares) | shares			(18,445)
Unvested at the end of period (in shares) | shares	320,663		320,663
Weighted Average Grant Price
Unvested at beginning of period (in dollars per share) | $ / shares			$ 112.48
Granted (in dollars per share) | $ / shares			113.03
Vested (in dollars per share) | $ / shares			111.81
Forfeited/cancelled (in dollars per share) | $ / shares			118.24
Unvested at the end of period (in dollars per share) | $ / shares	$ 112.68		$ 112.68
Weighted Average Remaining Contractual Term (Years)
Outstanding at the end of period (Years)			9 years 2 months 12 days
Aggregate Intrinsic Value
Unvested at the end of period (in dollars) | $	$ 25.6		$ 25.6
Share-based compensation expense (benefit) before tax | $	$ 3.8	$ 2.4	$ 9.8	$ 5.3
Weighted average remaining vesting period (in years)			2 years 1 month 6 days

Share-Based Compensation - STAP

Share-Based Compensation - STAP awards (Details) - STAP awards - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Awards granted
Grant expiration period from the grant date	4 years
Aggregate STAP liability	$ 18.3		$ 72.2
Weighted-average assumptions used to measure the fair value of the outstanding STAP awards:
Expected volatility (as a percent)	29.30%	33.40%
Risk-free interest rate (as a percent)	1.60%	2.50%
Expected term of awards (in years)	2 years 1 month 6 days	10 months 24 days
Closing price of common stock (in dollars per share)	$ 79.75	$ 127.88	$ 108.90
Share-based awards activity
Outstanding at January 1, 2018	2,867,979
Exercised (in shares)	(138,773)
Forfeited/cancelled (in shares)	(80,182)
Outstanding at December 31, 2018	2,649,024
Exercisable at December 31, 2018	2,639,024
Unvested at December 31, 2018	10,000
Share awards, Weighted Average Exercise Price
Outstanding at January 1, 2018	$ 107.85
Exercised (in dollars per share)	59.36
Forfeited (in dollars per share)	159.91
Outstanding at December 31, 2018	108.82
Exercisable at December 31, 2018	109.03
Unvested at December 31, 2018	$ 52.57
Share awards, Weighted Average Remaining Contractual Term (in Years)
Outstanding at December 31, 2018	4 years 3 months 18 days
Exercisable at December 31, 2018	4 years 3 months 18 days
Unvested at December 31, 2018	3 years 2 months 12 days
Share awards, Aggregate Intrinsic Value
Outstanding at December 31, 2018	$ 22.4
Exercisable at December 31, 2018	22.1
Unvested at December 31, 2018	$ 0.3

Share-Based Compensation - Sh_2

Share-Based Compensation - Share Tracking Awards Plans - Benefit recognized (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	1.4	32.2	(47)	(80.1)
Related income tax (benefit) expense	(0.2)	(7.4)	10.7	18.3
Share-based compensation expense (benefit), net of taxes	1.2	24.8	(36.3)	(61.8)
Cash payments on awards exercised during the period			6.9	71.5
Cost of product sales | STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	0.1	2	(1.9)	(4)
Research and development | STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	0.4	6.8	(9.9)	(15.2)
Selling, general and administrative | STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	$ 0.9	$ 23.4	$ (35.2)	$ (60.9)

Share-Based Compensation - Empl

Share-Based Compensation - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan	1 Months Ended
	Jun. 30, 2012shares
Share-based compensation expense
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

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income (loss)	$ 132.4	$ 106.5	$ (157.1)	$ 523.9
Denominator:
Weighted average outstanding shares - basic (in shares)	43.9	43.6	43.8	43.5
Effect of dilutive securities:
Stock options, restricted stock units and employee stock purchase plan (in shares)	0.1	0.4		0.5
Weighted average shares - diluted (in shares)	44	44	43.8	44
Net income (loss) per common share:
Basic (in dollars per share)	$ 3.02	$ 2.44	$ (3.59)	$ 12.04
Diluted (in dollars per share)	$ 3.01	$ 2.42	$ (3.59)	$ 11.91
Stock options and restricted stock units excluded from calculation (in shares)	8	4.5	7.1	4.6

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	Jan. 24, 2019	Jan. 31, 2019	Sep. 30, 2019	Sep. 30, 2018
Effective income tax rate (as a percent)			33.00%	21.00%
Unrecognized tax benefits			$ 0.9	$ 0.9
Positions of unrecognized tax benefits, if realized, would impact the effective tax rate			0.7	$ 0.7
Arena Pharmaceuticals, Inc.
One-time payment	$ 800	$ 800
Increase in deferred tax assets			$ 172.4

Segment Information - General (

Segment Information - General (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)segment	Sep. 30, 2018USD ($)
Net product sales, cost of product sales and gross profit by product
Net product sales	$ 401.5	$ 412.7	$ 1,137.7	$ 1,246.4
Cost of product sales	33	51.9	88.8	166.8
Gross profit	368.5	360.8	$ 1,048.9	1,079.6
Segment disclosures
Number of operating segments | segment			1
Remodulin
Net product sales, cost of product sales and gross profit by product
Net product sales	168.3	153.6	$ 479.6	439.9
Cost of product sales	5.5	4.4	16.1	10.8
Gross profit	162.8	149.2	463.5	429.1
Tyvaso
Net product sales, cost of product sales and gross profit by product
Net product sales	110.8	107.8	324.2	308.3
Cost of product sales	6.9	6.9	14.8	14.3
Gross profit	103.9	100.9	309.4	294
Orenitram
Net product sales, cost of product sales and gross profit by product
Net product sales	62	53.8	174.4	155.5
Cost of product sales	3.5	3.9	12.3	9.9
Gross profit	58.5	49.9	162.1	145.6
Unituxin
Net product sales, cost of product sales and gross profit by product
Net product sales	30.1	22.9	80.1	60.7
Cost of product sales	4.1	4.2	11.4	9.9
Gross profit	26	18.7	68.7	50.8
Adcirca
Net product sales, cost of product sales and gross profit by product
Net product sales	30.3	74.6	79.4	282
Cost of product sales	13	32.5	34.2	121.9
Gross profit	$ 17.3	$ 42.1	$ 45.2	$ 160.1

Segment Information - Geographi

Segment Information - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues from external customers by geographic area
Total revenues	$ 401.5	$ 412.7	$ 1,137.7	$ 1,246.4
United States
Revenues from external customers by geographic area
Total revenues	359.4	389	1,028.4	1,177.1
Rest-of-World
Revenues from external customers by geographic area
Total revenues	$ 42.1	$ 23.7	$ 109.3	$ 69.3

Segment Information - Concentra

Segment Information - Concentration Risk (Details) - item	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Information
Number of distributors			2
Net revenues | Customer concentration | Customer one
Segment Information
Concentration risk, percentage	53.00%	52.00%	55.00%	50.00%
Net revenues | Customer concentration | Customer two
Segment Information
Concentration risk, percentage	21.00%	18.00%	21.00%	17.00%

Arena License Agreement (Detail

Arena License Agreement (Details) - Arena Pharmaceuticals, Inc. - USD ($) $ in Millions	Jan. 24, 2019	Jan. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment	$ 800	$ 800
Marketing approval in the United States
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payment to be made upon marketing approval	250
Marketing approval in any of Japan, France, Italy, the United Kingdom, Spain or Germany
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payment to be made upon marketing approval	$ 150