Accumulated Other Comprehensive Income (AOCI) (Schedule of Items Reclassified to Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax effect	$ (15,364)	$ (14,405)	$ (27,818)	$ (21,881)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	32,354	34,054	41,463	63,244
Pension/postretirement settlements and curtailments	378	0	378	0
Prior service credit	(1,114)	(1,105)	(2,228)	(2,210)
Net actuarial loss	1,232	1,118	2,476	2,239
Total pretax amount reclassified	47,813	48,664	67,861	85,548
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	1,116	(420)	1,523	(872)
Income tax effect	(286)	108	(390)	223
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	830	(312)	1,133	(649)
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	(143)	(4)	(175)	(9)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income	353	9	451	20
Pension/postretirement settlements and curtailments	378	0	378	0
Prior service credit	(1,114)	(1,105)	(2,228)	(2,210)
Net actuarial loss	1,232	1,118	2,476	2,239
Total pretax amount reclassified	$ 496	$ 13	$ 626	$ 29