Accumulated Other Comprehensive Income (AOCI) (Schedule of Items Reclassified to Statement of Income) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Expense related to interest rate swaps included in Income before taxes		$ 5,016	$ 4,670
Total pretax amount reclassified		36,884	11,264
Income tax effect		7,476	3,365
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(29,190)	(7,662)
Prior service credit		(1,105)	(1,114)
Net actuarial loss		1,121	1,297
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative valuation adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Expense related to interest rate swaps included in Income before taxes	[1]	(452)	180
Income tax effect		115	(43)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(337)	137
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension and postretirement liability adjustments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total pretax amount reclassified	[2]	16	183
Income tax effect		(5)	(55)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		$ 11	$ 128

[1] Included in Interest expense, net, are payments related to the interest rate swap agreements and amortization of swap buyouts (see Notes 15 and 16).

[2] These accumulated other comprehensive income components are included in the computation of net periodic cost (see Note 4).