Accumulated Other Comprehensive Income (AOCI) (Schedule of Items Reclassified to Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax effect	$ (9,686)	$ (13,194)	$ (37,504)	$ (35,075)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	29,589	40,009	71,052	103,253
Pension/postretirement settlements and curtailments	0	0	378	0
Prior service credit	(1,114)	(1,105)	(3,342)	(3,315)
Net actuarial loss	1,244	1,118	3,720	3,357
Total pretax amount reclassified	39,276	53,319	107,137	138,867
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative valuation adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Expense/(income) related to interest rate swaps included in Income before taxes	1,219	(245)	2,742	(1,117)
Income tax effect	(311)	62	(701)	285
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	908	(183)	2,041	(832)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax effect	(32)	(4)	(207)	(13)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	98	9	549	29
Pension/postretirement settlements and curtailments	0	0	378	0
Prior service credit	(1,114)	(1,105)	(3,342)	(3,315)
Net actuarial loss	1,244	1,118	3,720	3,357
Total pretax amount reclassified	$ 130	$ 13	$ 756	$ 42