Income Taxes - Unrecognized Tax Benefits - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance as of beginning of period	$ 9,010	$ 10,823	$ 10,411
Additions for current year tax positions	3,316	1,180	2,925
Additions for tax positions of prior years	29	699	397
Reductions for tax positions of prior years	(85)	(472)	(44)
Reductions due to lapses of applicable statutes of limitations	(1,826)	(3,177)	(2,906)
Changes due to Tax Act			339
Reductions due to settlements with taxing authorities		(43)	(299)
Balance as of end of period	$ 10,444	$ 9,010	$ 10,823