Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the beginning and ending balance of unrecognized tax benefits
Balance at beginning of year	$ 9,799	$ 9,127	$ 9,105
Increase in unrecognized tax benefits as a result of tax positions taken during a prior period		215
Decrease in unrecognized tax benefits as a result of tax positions taken during a prior period	(502)		(132)
Reductions to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations		(334)	(543)
Increases in unrecognized tax benefits as a result of tax positions taken during the current period	747	791	697
Balance at end of year	10,044	9,799	9,127
Recorded as other long-term liability				$ 472	$ 409	$ 676
Recorded as a decrease in deferred tax assets				9,572	9,390	8,451
Unrecognized tax benefits	$ 10,044	$ 9,127	$ 9,105	$ 10,044	$ 9,799	$ 9,127