Employee Benefit Plans Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Deferred income tax benefit	$ 41,075		$ 22,920
AOCI	(144,084)	[1]	(97,821)	[1]
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	(8,370)		(9,729)
Net losses	(191,761)		(126,138)
Deferred income tax benefit	62,797		43,056
AOCI	(137,334)		(92,811)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	167		(532)
Net losses	(10,500)		(7,137)
Deferred income tax benefit	3,583		2,659
AOCI	$ (6,750)		$ (5,010)

[1] The increase in the unrecognized components of employee benefit plans was mainly due to actuarial losses resulting from a decrease in the discount rate from 5.25 percent as of December 31, 2010 to 4.20 percent as of December 31, 2011. See Note 20 — Employee Benefit Plans for additional information.