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, 2018	Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Expense related to interest rate swaps included in Income		$ 5,059	$ 4,625		$ 9,729		$ 9,060
Total pretax amount reclassified		37,337	3,012		52,428		20,536
Income tax effect		7,031	1,779		11,640		8,329
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(30,365)	(1,117)		(40,610)		(11,956)
Pension/postretirement curtailment		(518)			(518)
Prior service credit	[1]	(1,113)	(1,113)		(2,227)		(2,226)
Net actuarial loss	[1]	1,291	1,353		2,588		2,700
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	[2]	54	343		234		943
Income tax effect		(13)	(130)		(56)		(358)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		41	213		178		585
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		(340)	240	[3]	(157)	[4]	474	[4]
Income tax effect		102	(72)		47		(142)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		$ (238)	$ 168		$ (110)		$ 332

[1] These accumulated other comprehensive income components are included in Other expense, net (see Note 4). The curtailment adjustment was included in restructuring expenses, net.

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

[3] Included in Interest expense are payments related to the interest rate swap agreements and amortization of swap buyouts (see Note 15).

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