Income Taxes Expense - Reconciliation of the Beginning and Ending Amount of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 5,978	$ 8,848	$ 8,859
Gross increases related to current year tax positions	1,027	208	1,108
Gross increases related to prior year tax positions	221	0	0
Gross decreases related to prior year tax positions	0	(49)	(484)
Lapse of statute of limitations	(1,345)	(3,029)	(635)
Balance at end of period	$ 5,881	$ 5,978	$ 8,848