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	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Contractual interest expense	$ 1,446	$ 2,288	$ 3,602	$ 4,575
Amortization of debt discount	196	4,275	489	8,409
Amortization of debt issuance costs	11	160	26	315
Total interest expense	$ 1,653	$ 6,723	$ 4,117	$ 13,299

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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