Summary of Significant Accounting Policies - Liquidity - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Net loss	$ (29,764)	$ (29,508)	$ (67,132)	$ (128,860)
Accumulated deficit	$ 1,890,522		$ 1,890,522		$ 1,823,390

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details