Income Taxes - Reconciliation of unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning of period	$ 938	$ 847	$ 336
Gross increases - tax positions in current period	56	91	130
Gross increases - tax positions in prior period	0	0	381
Gross decreases - lapse of statute of limitations	(367)	0	0
Unrecognized tax benefits, end of period	627	938	$ 847
Unrecognized tax benefits that, if recognized, would impact effective tax rate	$ 600	$ 900