Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Schedule of Accumulated Comprehensive Income [Line Items]
Revenues	$ 937,497		$ 909,363
Interest expense	(24,064)		(28,991)
Tax benefit	(8,036)		(17,795)
Net income	49,267		72,100
Tax benefit	3,641		6,139
Reclassification out of Accumulated Other Comprehensive Income
Schedule of Accumulated Comprehensive Income [Line Items]
Revenues	(234)	[1]	(382)	[1]
Cost of sales	199	[1]	126	[1]
Interest expense	(507)	[1]	(507)	[1]
Total before tax	(542)	[1]	(763)	[1]
Tax benefit	210	[1]	297	[1]
Net income	(332)	[1]	(466)	[1]
Interest income	(347)	[1]	(2,612)	[1]
Tax benefit	128	[1]	966	[1]
Net of tax	219	[1]	1,646	[1]
Transition credit	2	[1],[2]	2	[1],[2]
Prior service costs	(27)	[1],[2]	(198)	[1],[2]
Actuarial losses	(9,758)	[1],[2]	(16,574)	[1],[2]
Total before tax	(9,783)	[1],[2]	(16,770)	[1],[2]
Tax benefit	3,641	[1],[2]	6,139	[1],[2]
Net of tax	$ (6,142)	[1],[2]	$ (10,631)	[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 15 for additional details).