Debt - Schedule of Equity Component of Debt (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Equity component of issuance of convertible senior notes	$ 30,346
Convertible debt \| Convertible Senior Notes
Debt Instrument [Line Items]
Equity component of issuance of convertible senior notes	30,346
Convertible debt \| Conversion option \| Convertible Senior Notes
Debt Instrument [Line Items]
Equity component of issuance of convertible senior notes	63,756
Convertible debt \| Payments for capped call transactions \| Convertible Senior Notes
Debt Instrument [Line Items]
Equity component of issuance of convertible senior notes	(31,412)
Convertible debt \| Issuance costs \| Convertible Senior Notes
Debt Instrument [Line Items]
Equity component of issuance of convertible senior notes	$ (1,998)

Amount of increase (decrease) in additional paid in capital (APIC) resulting from recognition of deferred taxes for convertible debt with a beneficial conversion feature.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=117331294&loc=d3e34017-109320

Name:	us-gaap_AdjustmentsToAdditionalPaidInCapitalConvertibleDebtWithConversionFeature
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration