Income Taxes - Deferred Tax Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Retirement benefits	$ 5,472	$ 8,236
Allowance for doubtful accounts	1,134	1,925
Insurance and litigation reserves	497	707
Postretirement benefits	1,056	1,623
Supplemental retirement benefits	2,679	3,670
Performance incentives	3,779	5,197
Equity-based compensation	1,071	2,088
Insurance settlement	4,581	7,755
Operating loss carryforward	8,602	7,343
Foreign tax credit and other credits	3,043	0
Uncertain tax positions	(410)	(101)
Restructuring	0	217
Other	2,816	2,834
Deferred Tax Assets, Gross, Total	34,320	41,494
Valuation allowance	(7,401)	(6,344)
Total deferred income tax assets, net	26,919	35,150
Depreciation	4,444	5,709
Europe Pension and Other	1,295	1,055
Amortization and other	15,373	16,012
Total deferred income tax liabilities	$ 21,112	$ 22,776