Debt - Schedule of Equity Component of Debt (Details) - Convertible debt - Convertible Senior Notes $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)
Debt Instrument [Line Items]
Conversion option	$ 63,756
Payments for capped call transactions	(31,412)
Issuance costs	1,998
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	$ 30,346

Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 25
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=51819886&loc=SL6014347-161799

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration