Summary of Significant Accounting Policies - Adoption of ASC 842 (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Convertible notes payable	$ 190,479		$ 213,645
Additional paid-in-capital	1,115,672		1,222,137
Accumulated deficit	$ (1,367,981)		(1,345,822)
Debt instrument, unamortized discount			88,100
Debt issuance costs			$ 3,200
Cumulative Effect, Period of Adoption, Adjustment | Adjustment due to ASU 2020-06 adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Convertible notes payable		$ 86,433
Additional paid-in-capital		(134,450)
Accumulated deficit		48,017
Cumulative Effect, Period of Adoption, Adjusted Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Convertible notes payable		300,078
Additional paid-in-capital		1,087,687
Accumulated deficit		(1,297,805)
Debt instrument, unamortized discount		4,700
Debt issuance costs		$ 300