Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Pension	$ 15,403	$ 16,256
Tax loss carryforwards	9,521	9,167
Inventory valuation	10,642	12,251
Other postretirement/postemployment costs	7,735	8,066
Accrued compensation	8,085	7,753
Lease obligation	9,846	9,188
Other	16,309	14,769
Valuation allowance	(3,757)	(3,592)
Total deferred tax assets	73,784	73,858
Deferred tax liabilities:
Depreciation and amortization	(109,391)	(110,230)
Goodwill	(9,850)	(9,757)
Swedish tax incentive	(9,170)	(7,436)
Right of use liability	(9,758)	(9,050)
Other	(5,191)	(4,558)
Total deferred tax liabilities	143,360	141,031
Non-current deferred tax assets	22,092	21,235
Non-current deferred tax liabilities	(91,668)	(88,408)
Net deferred tax liabilities	$ (69,576)	$ (67,173)