Income Taxes - Uncertain tax positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
A reconciliation of the beginning and ending liability for uncertain tax positions
Balance at beginning of year	$ 1,795	$ 3,531	$ 2,361
Increase Resulting from Current Period Tax Positions	131	21	97
Increases for tax position taken in prior years	15	146	1,602
Decreases due to settlements with taxing authorities		(693)	(8)
Decreases due to lapses in the statute of limitations	(722)	(1,210)	(521)
Balance at the end of year	1,219	1,795	$ 3,531
Unrecognized tax benefits that would affect the effective tax rate, if recognized	1,219
Accrued interest and penalties reported as income tax liability	$ 487	$ 502
U.S. corporate income tax rate		21.00%	35.00%
Net deferred tax liability			$ 22,452