Accumulated Other Comprehensive Income (Loss) (AOCI balances) (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	$ 2,915,145	$ 2,452,941	$ 2,490,698
Other Comprehensive (Loss) Income, Net of Tax	(136,837)	228,136	(78,194)
Reclassification of stranded tax effects to retained earnings as a result of tax reform		0
As of	2,916,782	2,915,145	2,452,941
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	535,555	236,486
Reclassification from accumulated other comprehensive income to retained earnings as a result of adoption of new guidance	(194,889)
Other comprehensive (loss) income before reclassifications	(105,634)	231,506
Net amount reclassified from accumulated other comprehensive income	(31,203)	(3,370)
Other Comprehensive (Loss) Income, Net of Tax	(136,837)	228,136
Reclassification of stranded tax effects to retained earnings as a result of tax reform		70,933
As of	203,829	535,555	236,486
Foreign Currency Translation Adjustments [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	6,314	(26,998)
Reclassification from accumulated other comprehensive income to retained earnings as a result of adoption of new guidance	0
Other comprehensive (loss) income before reclassifications	(35,584)	33,175
Net amount reclassified from accumulated other comprehensive income	0	137
Other Comprehensive (Loss) Income, Net of Tax	(35,584)	33,312	(22,149)
Reclassification of stranded tax effects to retained earnings as a result of tax reform		0
As of	(29,270)	6,314	(26,998)
Unrealized Gains (Losses) on Available- for- Sale Securities [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	194,889	92,931
Reclassification from accumulated other comprehensive income to retained earnings as a result of adoption of new guidance	(194,889)
Other comprehensive (loss) income before reclassifications	0	67,252	33,304
Net amount reclassified from accumulated other comprehensive income	0	0	1,127
Other Comprehensive (Loss) Income, Net of Tax	0	67,252	34,431
Reclassification of stranded tax effects to retained earnings as a result of tax reform		34,706
As of	0	194,889	92,931
Unrealized Gain (Loss) on Pensions and Other Postretirement Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	334,536	170,830
Reclassification from accumulated other comprehensive income to retained earnings as a result of adoption of new guidance	0
Other comprehensive (loss) income before reclassifications	(70,629)	131,108
Net amount reclassified from accumulated other comprehensive income	(31,071)	(3,629)	(9,850)
Other Comprehensive (Loss) Income, Net of Tax	(101,700)	127,479	(90,199)
Reclassification of stranded tax effects to retained earnings as a result of tax reform		36,227
As of	232,836	334,536	170,830
Cash Flow Hedge
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	(184)	(277)
Reclassification from accumulated other comprehensive income to retained earnings as a result of adoption of new guidance	0
Other comprehensive (loss) income before reclassifications	579	(29)
Net amount reclassified from accumulated other comprehensive income	(132)	122
Other Comprehensive (Loss) Income, Net of Tax	447	93	(277)
Reclassification of stranded tax effects to retained earnings as a result of tax reform		0
As of	$ 263	$ (184)	$ (277)