Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 4,394,147
Components of other comprehensive income (loss):
Before reclassifications to income and retained earnings	19,897
Reclassifications to income	5,826
Other comprehensive (loss) income	25,723	$ (127,823)
Balance at end of period	4,099,609	$ 5,098,303
Reclassifications before taxes, included in net periodic benefit expense	2,140
Reclassifications, income tax expense	450
Foreign Currency Translation Gains (Losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(324,011)
Components of other comprehensive income (loss):
Before reclassifications to income and retained earnings	19,897
Reclassifications to income	0
Other comprehensive (loss) income	19,897
Balance at end of period	(304,114)
Retirement and Postretirement Benefit Plan Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(275,632)
Components of other comprehensive income (loss):
Before reclassifications to income and retained earnings	0
Reclassifications to income	4,136
Other comprehensive (loss) income	4,136
Balance at end of period	(271,496)
Reclassifications before taxes, included in net periodic benefit expense	5,252
Deferred Loss on Interest Rate Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,690)
Components of other comprehensive income (loss):
Before reclassifications to income and retained earnings	0
Reclassifications to income	1,690
Other comprehensive (loss) income	1,690
Balance at end of period	0
Reclassifications, income tax expense	1,116
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(601,333)
Components of other comprehensive income (loss):
Balance at end of period	$ (575,610)