Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Accrued employee benefits and compensation	$ 4,269	$ 8,410
Tax loss and credit carryforwards	18,604	7,905
Reserves and accruals	4,935	4,699
Other	1,953	2,977
Total deferred tax assets	29,761	23,991
Less deferred tax asset valuation allowance	(16,889)	(8,754)	$ (6,388)	$ (6,202)
Total deferred tax assets, net of valuation allowance	12,872	15,237
Deferred tax liabilities
Depreciation and amortization	8,335	14,300
Postretirement benefit obligations	3,234	2,311
Unremitted earnings	1,778	3,100
Other	2,094	224
Total deferred tax liabilities	15,441	19,935
Net deferred tax asset (liability)	$ (2,569)	$ (4,698)