Debt - Summary of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Amortization of debt discount			$ 8,551	$ 9,073
Senior Notes | 2023 Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 1,581	$ 1,581	4,744	4,744
Amortization of debt discount	2,412	2,286	7,141	6,766
Total	$ 3,993	$ 3,867	$ 11,885	$ 11,510
Effective interest rate (as a percent)	5.45%		5.45%