Future Contributions, Benefit Payments and Subsidies (Details) (USD $)	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 20,200,000
Defined Benefit Plan, Expected Future Benefit Payments in Year One	22,426,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	22,811,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	23,082,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	23,508,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	23,893,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	127,895,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	4,000,000
Defined Benefit Plan, Expected Future Benefit Payments in Year One	6,892,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	7,062,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	7,188,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	7,298,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	7,371,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	37,682,000
Prescription Drug Subsidy Receipts, Year One	618,000
Prescription Drug Subsidy Receipts, Year Two	656,000
Prescription Drug Subsidy Receipts, Year Three	694,000
Prescription Drug Subsidy Receipts, Year Four	730,000
Prescription Drug Subsidy Receipts, Year Five	766,000
Prescription Drug Subsidy Receipts, Five Fiscal Years Thereafter	$ 4,322,000