Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension and postretirement benefits [Abstract]
Amortization of net actuarial loss, Gross Amount	[1]	$ 926	$ 2,317	$ 3,760
Amortization of net actuarial loss, Income Tax Provision	[1]	(236)	(585)	(1,417)
Amortization of net actuarial loss, Net Amount	[1]	690	1,732	2,343
Actuarial gains (losses), Gross Amount	[1]	(6,548)	7,322	25,776
Actuarial gains (losses), Income Tax (Provision) Benefit	[1]	1,655	(1,416)	(9,371)
Actuarial gains (losses), Net Amount	[1]	(4,893)	5,906	16,405
Foreign currency translation adjustments, Gross Amount		(85)	(819)	(146)
Foreign currency translation, Income Tax Provision		0	0	0
Foreign currency translation adjustments, Net Amount		(85)	(819)	(146)
Total other comprehensive income, Gross Amount		(5,707)	8,820	29,390
Total other comprehensive income, Income Tax Provision		1,419	(9,926)	(10,788)
Total other comprehensive income (loss), net of taxes		(4,288)	(1,106)	18,602
ASU 2018-02 [Member]
Pension and postretirement benefits [Abstract]
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	(7,925)	0
Reclassification to retained earnings of stranded tax effects from tax reform, Net Amount		$ 0	$ (7,925)	$ 0

[1] The discount rate for the Higman pension plan in 2018 was changed from 4.13% as of February 14, 2018 and 4.02% as of March 31, 2018 to 4.40% as of December 31, 2018.Actuarial gains (losses) are amortized into other income (expense). (See Note 11 – Retirement Plans)