Convertible Senior Notes - Summary of Outstanding Note Balances (Details) - Notes - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 17, 2014
Debt Instrument [Line Items]
Principal	$ 345,000	$ 345,000	$ 345,000
Less: debt discount and debt issuance costs, net	(31,321)	(36,195)
Net carrying amount	313,679	308,805
Equity component	$ 61,195	$ 61,195

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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Face (par) amount of debt instrument at time of issuance.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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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.

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