Income Taxes - Deferred Tax Balances (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement benefits	$ 15,237,000	$ 15,142,000
Allowance for doubtful accounts	2,316,000	2,253,000
Insurance and litigation reserves	842,000	1,002,000
Performance incentives	5,914,000	7,213,000
Equity-based compensation	1,282,000	1,050,000
Prepaid expense	756,000	2,976,000
Insurance settlement	0	3,895,000
Operating loss carryforward	16,693,000	16,044,000
Foreign tax credit and other credits	24,873,000	34,384,000
Interest	16,812,000	11,479,000
Restructuring reserves	1,121,000	2,167,000
Right of use lease assets	9,346,000	10,015,000
Royalties and license fees	0	2,156,000
Inventory reserves	2,225,000	2,163,000
Research and development	7,974,000	2,580,000
Other	3,005,000	1,317,000
Total deferred tax assets, gross	108,396,000	115,836,000
Valuation allowance	(21,511,000)	(13,834,000)	$ (7,520,000)	$ (7,401,000)
Total deferred tax assets, net	86,885,000	102,002,000
Depreciation	15,473,000	17,754,000
Foreign pension and other	1,807,000	1,269,000
Amortization and other	222,794,000	254,359,000
Lease liabilities	9,151,000	9,965,000
Outside basis in equity investment	7,938,000	6,776,000
Unremitted earnings	5,919,000	8,228,000
Total deferred tax liabilities	$ 263,082,000	$ 298,351,000