Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating Loss Carryforwards [Line Items]
Deferred tax liabilities	$ 2,574		$ 2,574
Domestic
Operating Loss Carryforwards [Line Items]
Taxable loss	(24,700)	$ (26,900)	(82,200)	$ (133,900)
Operating loss carryforwards	836,600		836,600
Deferred tax assets, capital loss carryforwards	212,500		212,500
Research and development tax credits	10,900		10,900
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	76,800		76,800
Generated After 2017
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 583,900		$ 583,900