Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.9-03(16))
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Convertible Debt - Schedule of Outstanding Principal Amount and Carrying Value of Notes (Details) - USD ($)	Sep. 30, 2019	Aug. 19, 2019	Dec. 31, 2018	Nov. 30, 2018	Nov. 19, 2018	Sep. 15, 2017
Debt Instrument [Line Items]
Net carrying amount	$ 1,435,927,000		$ 738,904,000
Convertible Debt \| 2017 Notes
Debt Instrument [Line Items]
Principal	431,250,000		431,250,000			$ 431,250,000
Unamortized debt discount	(64,963,000)		(79,911,000)
Net carrying amount	366,287,000		351,339,000
Convertible Debt \| 2018 Notes
Debt Instrument [Line Items]
Principal	575,000,000		575,000,000	$ 575,000,000.0	$ 500,000,000.0
Unamortized debt discount	(168,012,000)		(187,435,000)
Net carrying amount	406,988,000		$ 387,565,000
Convertible Debt \| 2019 Notes
Debt Instrument [Line Items]
Principal	948,750,000	$ 948,750,000
Unamortized debt discount	(286,098,000)
Net carrying amount	$ 662,652,000