Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension and postretirement benefits [Abstract]
Amortization of net actuarial loss, Gross Amount	[1]	$ 2,317	$ 3,760	$ 4,763
Amortization of net actuarial loss, Income Tax (Provision) Benefit	[1]	(585)	(1,417)	(1,825)
Amortization of net actuarial loss, Net Amount	[1]	1,732	2,343	2,938
Actuarial gains (losses), Gross Amount	[1]	7,322	25,776	(15,013)
Actuarial gains (losses), Income Tax (Provision) Benefit	[1]	(1,416)	(9,371)	5,754
Actuarial gains (losses), Net Amount	[1]	5,906	16,405	(9,259)
Foreign currency translation adjustments, Gross Amount		(819)	(146)	0
Foreign currency translation adjustments, Income Tax (Provision) Benefit		0	0	0
Foreign currency translation adjustments, Net Amount		(819)	(146)	0
Total other comprehensive income, Gross Amount		8,820	29,390	(10,250)
Total other comprehensive income, Income Tax (Provision) Benefit		(9,926)	(10,788)	3,929
Total other comprehensive income (loss), net of taxes		(1,106)	18,602	(6,321)
ASU 2018-02 [Member]
Pension and postretirement benefits [Abstract]
Adoption of ASU 2018-02 - reclassification to retained earnings, Gross Amount		0	0	0
Adoption of ASU 2018-02 - reclassification to retained earnings, Income Tax (Provision) Benefit		(7,925)	0	0
Adoption of ASU 2018-02 - reclassification to retained earnings, Net Amount		$ (7,925)	$ 0	$ 0

[1] Actuarial gains (losses) are amortized into other income (expense). (See Note 11 - Retirement Plans)