Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension and postretirement benefits [Abstract]
Amortization of net actuarial loss, Gross Amount	[1]	$ 1,912	$ 926	$ 2,317
Amortization of net actuarial loss, Income Tax (Provision) Benefit	[1]	(483)	(236)	(585)
Amortization of net actuarial loss, Net Amount	[1]	1,429	690	1,732
Actuarial gains (losses), Gross Amount	[1]	(31,755)	(6,548)	7,322
Actuarial gains (losses), Income Tax (Provision) Benefit	[1]	7,006	1,655	(1,416)
Actuarial gains (losses), Net Amount	[1]	(24,749)	(4,893)	5,906
Reclassification to retained earnings of stranded tax effects from tax reform, Gross Amount		0	0	0
Adoption of ASU 2018-02 - reclassification to retained earnings, Income Tax (Provision) Benefit		0	0	(7,925)
Reclassification to retained earnings of stranded tax effects from tax reform, Net Amount		0	0	(7,925)
Foreign currency translation adjustments, Gross Amount		(333)	(85)	(819)
Foreign currency translation, Income Tax (Provision) Benefit		0	0	0
Foreign currency translation adjustments, Net Amount		(333)	(85)	(819)
Total other comprehensive income, Gross Amount		(30,176)	(5,707)	8,820
Total other comprehensive income, Income Tax (Provision) Benefit		6,523	1,419	(9,926)
Total other comprehensive loss, net of taxes		$ (23,653)	$ (4,288)	$ (1,106)

[1] Actuarial gains (losses) are amortized into other income (expense). (See Note 12 – Retirement Plans)