Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Accrued employee benefits and compensation	$ 8,410	$ 9,899
Postretirement benefit obligations	0	3,335
Tax loss and credit carryforwards	7,905	7,146
Reserves and accruals	4,699	6,361
Other	2,977	2,792
Total deferred tax assets	23,991	29,533
Less deferred tax asset valuation allowance	(8,754)	(6,388)		$ (6,202)	$ (7,691)
Deferred tax liabilities, undistributed foreign earnings			$ 6,100
Total deferred tax assets, net of valuation allowance	15,237	23,145
Deferred tax liabilities
Depreciation and amortization	14,300	14,965
Postretirement benefit obligations	2,311	0
Unremitted earnings	3,100	7,239
Other	224	190
Total deferred tax liabilities	19,935	22,394
Net deferred tax asset	$ (4,698)	$ 751