Accumulated Other Comprehensive Income (Loss) (Components of OCI) (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Before Tax	$ 133,553	$ (174,347)	$ 319,059
Other Comprehensive Income (Loss), Income Tax	(34,087)	37,510	(90,923)
Other Comprehensive Income (Loss), Net of Tax	99,466	(136,837)	228,136
Foreign Currency Translation Adjustment [Member]
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	5,371		33,175
Other Comprehensive Income (Loss) before Reclassifications, Tax	0		0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	5,371	(35,584)	33,175
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	2,011		137
Reclassification from AOCI, Current Period, Tax	0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,011	0	137
Other Comprehensive Income (Loss), Before Tax	7,382	(35,584)	33,312
Other Comprehensive Income (Loss), Income Tax	0	0	0
Other Comprehensive Income (Loss), Net of Tax	7,382	(35,584)	33,312
Unrealized Gains (Losses) on Available- for- Sale Securities [Member]
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Before Tax			112,086
Other Comprehensive Income (Loss), Income Tax			(44,834)
Other Comprehensive Income (Loss), Net of Tax	0	0	67,252
Pension and Other Postretirement Plans [Member]
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	164,527	(70,629)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(97,864)	(42,563)	(6,050)
Reclassification from AOCI, Current Period, Tax	26,422	11,492	2,421
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(71,442)	(31,071)	(3,629)
Other Comprehensive Income (Loss), Before Tax	127,515	(139,314)	173,549
Other Comprehensive Income (Loss), Income Tax	(34,430)	37,614	(46,070)
Other Comprehensive Income (Loss), Net of Tax	93,085	(101,700)	127,479
Net Actuarial Loss [Member]
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	231,104	(101,013)	179,674
Other Comprehensive Income (Loss) before Reclassifications, Tax	(62,398)	27,273	(48,511)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	168,706	(73,740)	131,163
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(2,046)	(11,349)	(6,527)	[1]
Reclassification from AOCI, Current Period, Tax	552	3,064	2,612
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1,494)	(8,285)	(3,915)
Net Prior Service Cost [Member]
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(5,725)	4,262	(75)
Other Comprehensive Income (Loss) before Reclassifications, Tax	1,546	(1,151)	20
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(4,179)	3,111	(55)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(4,142)	(947)	477	[1]
Reclassification from AOCI, Current Period, Tax	1,118	256	(191)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(3,024)	(691)	286
Curtailments and settlements Included in Net Income [Member]
Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(91,676)	(30,267)	0	[1]
Reclassification from AOCI, Current Period, Tax	24,752	8,172
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(66,924)	(22,095)
Cash Flow Hedges
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(906)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(95)
Other Comprehensive Income (Loss), Before Tax	(1,344)
Other Comprehensive Income (Loss), Income Tax	343
Other Comprehensive Income (Loss), Net of Tax	$ (1,001)
Cash Flow Hedges
Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		579
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(132)
Other Comprehensive Income (Loss), Before Tax		551	112
Other Comprehensive Income (Loss), Income Tax		(104)	(19)
Other Comprehensive Income (Loss), Net of Tax		$ 447	$ 93

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension and postretirement plan cost (see Note 15) and are included in non-operating pension and postretirement benefit income in the Company’s Consolidated Statements of Operations.