Debt - Summary of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Amortization of debt discount			$ 8,666	$ 2,604
Senior Notes \| Convertible Note Due 2023
Debt Instrument [Line Items]
Contractual interest expense	$ 1,581	$ 720	4,743	720
Amortization of debt discount	2,166	938	6,411	938
Total	$ 3,747	$ 1,658	$ 11,154	$ 1,658
Effective interest rate (as a percent)	5.45%		5.45%

Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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