Accumulated Other Comprehensive Income (AOCI) (Schedule of Items Reclassified to Statement of Income) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Payments made on interest rate swaps included in Income before taxes		$ 2,238	$ 2,676
Total pretax amount reclassified		(20,359)	(20,758)
Income tax effect		7,043	8,519
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(13,501)	(12,213)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Valuation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Payments made on interest rate swaps included in Income before taxes	[1]	281	486
Income tax effect		(107)	(190)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		174	296
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]	165	396
Income tax effect		(49)	(139)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		116	257
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total pretax amount reclassified		(1,113)	(1,109)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total pretax amount reclassified		$ 1,278	$ 1,505

[1] Included in Interest expense.

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