Income Taxes - Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of unrecognized tax benefits
Balance at the beginning of the year	$ 0	$ 3,088	$ 0
Additions for current year tax positions	0	0	7,719
Reductions for current year tax positions	0	0	(4,631)
Additions for prior year tax positions	0	4,631	0
Reductions for prior year tax positions	0	(7,719)	0
Balance at the end of the year	$ 0	$ 0	$ 3,088