Income Taxes - Deferred Income Tax Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
U.S. foreign tax credit		$ 7,027
Stock and long-term compensation plans	$ 1,855	2,304
Foreign NOL & other carryforwards	20,864	16,340
US state NOL carryforwards	823	803
US alternative minimum tax		357
Deferred revenue	1,278	358
Pension liability, net	974	1,038
Reserve for uncertain tax issues		(445)
Amortization and depreciation	753	708
Accrued expenses and other	1,246	523
Total gross deferred tax assets	27,793	29,013
Less: Valuation allowance	(12,805)	(6,274)
Net deferred income tax assets	14,988	22,739
Deferred tax liabilities:
Accruals	506	691
US tax on unremitted foreign earnings		424
Foreign tax on unremitted foreign earnings	7,434
Intangible assets	9,341	10,947
Deferred tax liabilities	17,281	12,062
Net deferred tax assets		$ 10,677
Net deferred tax liabilities	$ (2,293)