Income Taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Recognized tax benefit	$ 2,800
Accrued interest and penalties on unrecognized tax benefits	2,100	$ 2,300
Interest and penalties recorded on unrecognized tax benefits	(200)
Reconciliation of total amounts of unrecognized tax benefits
Balance at beginning of the period	1,476	1,047	$ 999
Gross increases - tax positions in prior period	1,378	301	48
Gross decreases - tax positions in prior period	(10)
Gross increases - tax positions in current period	1,470	128
Balance at end of the period	4,314	1,476	$ 1,047
Deferred taxes provided for withholding or other taxes for repatriation of foreign earnings	0
Undistributed earnings from foreign subsidiaries	105,200
Foreign withholding taxes on the undistributed earnings	6,300
Undistributed Foreign Earnings	$ 1,600	$ 4,700