Income Taxes - Valuation allowances, uncertain tax positions and accrued interest and penalties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation allowance
Increase (decrease) in valuation allowance	$ 2,100	$ 2,400
Interest and penalties
Accrued interest or penalties for income tax liabilities	200	100	$ 100
Change in reserve for uncertain tax benefits
Reserve at beginning of year	427	107	662
Increases related to prior year tax positions	2,500	427	7
Lapse of statute of limitations	(4)	(107)	(562)
Total	2,923	$ 427	$ 107
Uncertain tax positions
Uncertain tax positions that would impact of effective tax rate	2,100
Unrecognized tax benefits estimated decrease	$ 2,700