Income Taxes (Schedule of Components of Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Pensions	$ 37,423	$ 35,066
Other postretirement employee benefits	13,002	13,834
Net operating loss carryforwards	983	6,935
Inventories	443	2,325
Tax credits	2,207	2,123
Nondeductible accruals	2,067	2,041
Incentive compensation	1,643	2,009
Employee benefits	1,444	1,769
Other	120	116
Total deferred tax assets	59,332	66,218
Valuation allowance	(650)	(488)	$ 0
Deferred tax assets, net of valuation allowance	58,682	65,730
Timber and timberlands, net	(2,165)	(5,010)
Property, plant and equipment, net	(14,018)	(14,120)
Other	(448)
Total deferred tax liabilities	(16,631)	(19,130)
Net deferred tax assets	$ 42,051	$ 46,600