Accumulated Other Comprehensive Loss (Reclassifications) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Gains (losses) on cash flow hedges
Revenues	$ 890,681		$ 937,497
Interest expense	(24,064)		(24,064)
Tax benefit	(50,547)		(8,036)
Net income	85,206		49,267
Pension and Postretirement Benefit Plans
Tax benefit	(4,167)		(3,641)
Reclassification out of Accumulated Other Comprehensive Income
Gains (losses) on cash flow hedges
Revenues	(396)	[1]	(234)	[1]
Cost of sales	(395)	[1]	199	[1]
Interest expense	(507)	[1]	(507)	[1]
Total before tax	(1,298)	[1]	(542)	[1]
Tax benefit	(502)	[1]	(210)	[1]
Net income	(796)	[1]	(332)	[1]
Gains (losses) on available for sale securities
Unrealized losses	(24)	[1]	(347)	[1]
Tax benefit	(9)	[1]	(128)	[1]
Net of tax	(15)	[1]	(219)	[1]
Pension and Postretirement Benefit Plans
Transition credit	2	[1],[2]	2	[1],[2]
Prior service costs	(59)	[1],[2]	(27)	[1],[2]
Actuarial losses	(11,519)	[1],[2]	(9,758)	[1],[2]
Total before tax	(11,576)	[1],[2]	(9,783)	[1],[2]
Tax benefit	(4,167)	[1],[2]	(3,641)	[1],[2]
Net of tax	$ (7,409)	[1],[2]	$ (6,142)	[1],[2]

[1] Amounts in parentheses indicate debits (reductions) to income.

[2] These items are included in the computation of net periodic costs of defined benefit pension plans and nonpension postretirement benefit plans (see Note 11 for additional details).