Benefit Plans Benefit Plans - Textuals (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Period of Return for Fixed Income Investments From Discount Rate Assumptions	20 years
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 23,318	$ 15,505
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	15,814
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amount of net prior service cost (credit)	258
Amount of net loss	15,798
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	2,247	2,223
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	1,940
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amount of net prior service cost (credit)	(517)
Amount of net loss	$ 488