Income Taxes - Activity in Valuation Allowance (Details) - Deferred tax asset valuation allowance - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation allowance activities
Balance at Beginning of Year	$ 2,065	$ 8,930	$ 8,754
Provision	47	238	204
Released		7,103	28
Balance at End of Year	$ 2,112	$ 2,065	$ 8,930