Accumulated Other Comprehensive Income Reclassifications in AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income taxes	$ 263,018		$ 125,200	$ 684,100		$ 436,461
Provision for income taxes	(92,728)		(38,236)	(244,647)		(146,183)
Net income	170,290		86,964	439,453		290,278
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	(95)	[1]		(286)	[1]
Net loss	(600)	[1]		(1,718)	[1]
Income before income taxes	(695)			(2,004)
Provision for income taxes	267			771
Net income	$ (428)			$ (1,233)

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 8 (Employee Benefits) to the financial statements included in the 2012 Form 10-K.