Retirement Plans, Defined Contribution Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan [Member]
Defined Contribution Pension and Other Postretirement Benefit Expense [Abstract]
Percentage of matching contributions under defined contribution plan	4.00%
Total expense for defined contribution plans	$ 6,100	$ 6,000	$ 6,000
Pension Plan [Member]
Benefit obligation [Roll Forward]
Benefit obligation at beginning of year	39,421	34,152
Service cost	1,601	1,432	1,465
Interest cost	1,022	1,273	1,137
Foreign currency exchange rate changes	690	558
Benefits paid	(1,948)	(1,899)
Amendments	42	0
Actuarial loss	4,803	3,905
Benefit obligation at end of year	45,631	39,421	34,152
Change in fair value of plan assets [Roll Forward]
Plan assets at beginning of year	31,776	28,299
Company contributions	1,117	1,086
Foreign currency exchange rate changes	882	968
Benefits paid	(1,948)	(1,899)
Actual gain on plan assets	3,849	3,322
Plan assets at end of year	35,676	31,776	28,299
Funded status	(9,955)	(7,645)
Accumulated benefit obligation	44,559	38,596
Amounts recognized in Consolidated Balance Sheets [Abstract]
Accrued employee and retiree benefits	(19,349)	(17,143)
Other accrued expenses	(722)	(710)
Other assets	10,116	10,208
Net liability	(9,955)	(7,645)
Components of annual benefit cost [Abstract]
Service cost	1,601	1,432	1,465
Interest cost	1,022	1,273	1,137
Expected return on plan assets	(813)	(896)	(896)
Recognized actuarial loss (gain)	41	(176)	(141)
Settlement income	0	0	(179)
Defined benefit expense	$ 1,851	$ 1,633	$ 1,386
Weighted average liability assumptions [Abstract]
Discount rate	1.87%	2.69%
Expected return on plan assets	2.17%	2.68%
Rate of compensation increase	0.34%	0.34%
Weighted average cost assumption [Abstract]
Discount rate	2.69%	3.80%	3.16%
Expected return on plan assets	2.68%	3.21%	3.03%
Rate of compensation increase	0.34%	0.31%	0.33%
Estimated Future Benefit Payments [Abstract]
2021	$ 1,600
2022	3,900
2023	1,600
2024	4,000
2025	1,700
2026 through 2030	11,700
Estimated future employer contributions for next fiscal year	1,200
Amounts recognized in Accumulated Other Comprehensive Loss [Abstract]
Unrecognized net actuarial loss	2,402	$ 683
Prior service cost	187	146
Total before tax effects	2,589	829
Other Comprehensive Income (Loss), Pension Adjustment, Net of Tax [Abstract]
Net actuarial (loss) gain arising during the period	(1,293)	(1,091)	$ 1,257
Prior service cost	(32)	0	(127)
Amortization of actuarial loss (gain), included in defined benefit expense	32	(130)	(103)
Pension adjustment, net of tax	$ (1,293)	$ (1,221)	$ 1,027