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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Payments made on interest rate swaps included in income before taxes		$ 3,691	$ 2,702	$ 5,929	$ 5,378
Total pretax amount reclassified		16,183	(2,484)	36,542	18,274
Income tax effect		6,082	(364)	13,125	8,155
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		(10,367)	2,172	(23,868)	(10,041)
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]	305	467	586	953
Income tax effect		(116)	(182)	(223)	(372)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		189	285	363	581
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]	184	350	349	746
Income tax effect		(56)	(122)	(105)	(261)
Effect on net income due to items reclassified from Accumulated Other Comprehensive Income		128	228	244	485
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		(1,112)	(1,111)	(2,225)	(2,220)
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		$ 1,296	$ 1,461	$ 2,574	$ 2,966

[1] Included in Interest expense.

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