Income Taxes (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred tax assets:
Pension	$ 19,025		$ 13,255
Tax loss carryforwards	11,516		16,078
Inventory valuation	11,576		10,568
Other postretirement/postemployment costs	8,372		9,440
Accrued Compensation	9,384		5,743
Other	3,349		4,018
Valuation allowance	(4,366)		(10,223)
Total deferred tax assets	58,856		48,879
Deferred tax liabilities:
Depreciation and amortization	(122,636)		(82,422)
Goodwill	(9,597)		(9,440)
Other	(12,708)		(18,361)
Total deferred tax liabilities	144,941		110,223
Non-current deferred tax assets	20,474	$ 11,171	12,161
Non-current deferred tax liabilities	(106,559)	$ (73,891)	(73,505)
Net deferred tax liabilities	$ (86,085)		$ (61,344)