Income Taxes (Components of Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred income tax assets:
Pension	$ 11,799	$ 9,644
Non-pension postretirement benefits	22,810	21,751
Other accrued liabilities	19,244	20,432
Receivables	2,756	2,341
Net operating loss and charitable contribution carry forwards	16,861	25,754
Tax credits	11,502	10,245
Total deferred income tax assets	84,972	90,167
Deferred income tax liabilities:
Property, plant and equipment	23,921	22,882
Inventories	3,866	2,378
Intangibles and other	5,255	7,883
Total deferred income tax liabilities	33,042	33,143
Net deferred income tax asset (liability):
Net deferred income tax asset before valuation allowance	51,930	57,024
Valuation allowance	(13,773)	(11,184)	$ (66,486)	$ (46,048)
Net deferred income tax asset (liability)	$ 38,157	$ 45,840