Convertible Notes Payable - Summary of Total Interest Expense Recognized Related to the Convertible Notes (Details) - Convertible debt - 3.00% Convertible notes - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 2,287	$ 2,287
Amortization of debt discount	4,134	3,614
Amortization of debt issuance costs	155	136
Total interest expense	$ 6,576	$ 6,037

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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