Income Taxes (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Pension	$ 13,255	$ 27,410
Tax loss carryforwards	16,078	16,686
Inventory valuation	10,568	15,518
Other postretirement/postemployment costs	9,440	14,071
Accrued Compensation	5,743	10,121
Other	4,018	6,489
Valuation allowance	(10,223)	(14,957)
Total deferred tax assets	48,879	75,338
Deferred tax liabilities:
Depreciation and amortization	82,422	89,198
Goodwill	(9,440)	(14,871)
Other	(18,361)	(12,282)
Total deferred tax liabilities	110,223	116,351
Non-current deferred tax assets	12,161	25,433
Non-current deferred tax liabilities	73,505	66,446
Net deferred tax liabilities	$ (61,344)	$ (41,013)