Debt - Schedule of Debt (Details) - USD ($)	1 Months Ended
	May 31, 2013	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Current portion of long-term debt		$ 297,054,000	$ 0
Long-term debt, non-current		292,457,000	278,792,000
Convertible Senior Notes
Debt Instrument [Line Items]
Principal	$ 300,000,000.0	300,000,000	300,000,000
Less: debt issuance costs, debt discount, net of amortization		(5,946,000)	(21,208,000)
Long-term debt		294,054,000	278,792,000
Equity component		63,510,000	$ 63,510,000
Debt issuance costs attributable to the equity component	$ 1,700,000
Term Loan
Debt Instrument [Line Items]
Principal		300,000,000
Less: debt issuance costs, debt discount, net of amortization		(4,543,000)
Long-term debt		295,457,000
Current portion of long-term debt		3,000,000
Long-term debt, non-current		$ 292,457,000