Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets
Accrued employee benefits and compensation	$ 9,284	$ 9,168
Postretirement benefit obligations	5,434	7,866
Tax loss and credit carryforwards	9,318	16,533
Reserves and accruals	5,075	4,230
Depreciation and amortization	0	17,862
Other	3,474	2,550
Total deferred tax assets	32,585	58,209
Less deferred tax asset valuation allowance	(6,202)	(7,691)	$ (7,302)	$ (7,992)
Total deferred tax assets, net of valuation allowance	26,383	50,518
Deferred tax liabilities
Depreciation and amortization	17,492	14,303
Other	187	344
Total deferred tax liabilities	17,679	14,647
Net deferred tax asset	$ 8,704	$ 35,871