Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of unrecognized tax benefits
Balance at the beginning of the period	$ 1,895	$ 1,119	$ 1,107
Additions based on tax positions related to prior years	0	660	204
Reductions based on tax positions related to prior years	(171)	(1)	0
Additions for tax positions of the current year	100	319	155
Lapse of statute of limitations	(67)	(202)	(347)
Balance at the end of the period	1,757	1,895	1,119
Portion of uncertain tax benefit, if recognized, would reduce effective tax rate	100	0	0
Increase (decrease) in accrued interest as a result of the reversal of accrued interest associated with the lapse of statutes of limitations	5	200	(61)
Interest accrued on unrecognized tax benefits	$ 400	$ 400	$ 200