Convertible Notes Payable - Summary of Outstanding Balances of Convertible Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Aug. 14, 2017
Debt Instrument [Line Items]
Net carrying amount	$ 183,556	$ 179,806
Convertible debt \| 3.00% Convertible notes
Debt Instrument [Line Items]
Principal	305,000		$ 305,000
Less: debt discount and issuance costs, net	(121,444)
Net carrying amount	183,556		166,300
Equity component	$ 134,450		$ 138,700

Long Term Debt, Gross Excluding Interest

No definition available.

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- Definition

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

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

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

+ References

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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