Income Taxes - Statutory Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Statutory tax rate percentage	35.00%	34.00%	34.00%
Reconciliation of statutory tax and provision
Expected tax at statutory rate	$ 2,933	$ 3,884	$ 17,305
Foreign taxes at other rates	(3,139)	(7,512)	(12,487)
US tax on foreign earnings, net of foreign tax credits	(226)	(405)	1,968
Valuation reserves on NOL carryforwards	3,997	3,816	469
US tax reform - deemed repatriation	18,472
US tax reform - changes in indefinite reinvestment assertion	7,281
US tax reform - deferred tax expense from tax rate change	2,339
State income taxes, net of federal benefit	(59)	83	26
Disallowed expenses and other	(818)	997	1,423
Total	$ 30,780	$ 863	$ 8,704