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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Expense related to interest rate swaps included in Income before taxes		$ 5,200	$ 4,784	$ 14,929	$ 13,843
Total pretax amount reclassified		39,975	19,029	92,403	39,565
Income tax effect		11,491	3,809	23,131	12,138
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(28,215)	(15,269)	(68,825)	(27,225)
Pension/postretirement curtailment gain	[1]	(232)		(750)
Prior service credit	[2]	(1,114)	(1,113)	(3,341)	(3,339)
Net actuarial loss	[2]	1,294	1,350	3,882	4,050
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	[3]	(96)	295	138	1,238
Income tax effect		23	(112)	(33)	(470)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(73)	183	105	768
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		(52)	237	(209)	711
Income tax effect		16	(71)	63	(213)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		$ (36)	$ 166	$ (146)	$ 498

[1] The curtailment adjustment was included in restructuring expenses, net (see Note 5).

[2] These accumulated other comprehensive income components are included in Other (income)/expense, net (see Note 4).

[3] Included in Interest expense are payments related to the interest rate swap agreements and amortization of swap buyouts (see Note 16).