Income Taxes - Uncertain tax position liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1	$ 4,810	$ 4,278
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	490	532
Balance, December 31	$ 5,300	$ 4,810