Accumulated Other Comprehensive Loss (Reclassifications) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gains (losses) on cash flow hedges
Revenues		$ 835,886	$ 880,891	$ 1,680,475	$ 1,771,572
Interest expense, net		(20,799)	(20,971)	(40,100)	(45,035)
Benefit from income tax		(33,394)	(52,351)	(70,418)	(102,898)
Net income		58,184	156,363	120,824	241,569
Pension and Postretirement Benefit Plans
Benefit from income tax		4,122	3,614	7,921	7,781
Reclassification out of Accumulated Other Comprehensive Loss
Gains (losses) on cash flow hedges
Revenues	[1]	(353)	(432)	(733)	(828)
Cost of sales	[1]	145	(190)	370	(585)
Interest expense, net	[1]	(507)	(507)	(1,014)	(1,014)
Total before tax	[1]	(715)	(1,129)	(1,377)	(2,427)
Benefit from income tax	[1]	277	436	535	938
Net income	[1]	(438)	(693)	(842)	(1,489)
Gains (losses) on available for sale securities
Interest expense, net	[1]	(19)	(18)	(1)	(42)
Benefit from income tax	[1]	7	7	0	16
Net of tax	[1]	(12)	(11)	(1)	(26)
Pension and Postretirement Benefit Plans
Transition credit	[1],[2]	2	3	4	5
Prior service costs	[1],[2]	(41)	(61)	(83)	(120)
Actuarial losses	[1],[2]	(9,361)	(10,056)	(19,868)	(21,595)
Total before tax	[1],[2]	(9,400)	(10,114)	(19,947)	(21,710)
Benefit from income tax	[1],[2]	4,122	3,614	7,919	7,781
Net of tax	[1],[2]	$ (5,278)	$ (6,500)	$ (12,028)	$ (13,929)

[1] Amounts in parentheses indicate reductions to income and increases to other comprehensive income (loss).

[2] Reclassified from accumulated other comprehensive loss into selling, general and administrative expenses. These amounts are included in the computation of net periodic costs (see Note 10 for additional details).