Nonqualified Benefit Plans (Details) (Supplemental Employee Retirement Plans, Defined Benefit [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 76,900,000	$ 77,500,000
Net periodic benefit cost	8,100,000	7,800,000	8,800,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation	113,800,000	99,400,000
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation	105,700,000	93,200,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.00%	5.11%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	4.00%	4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.11%	5.75%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	4.00%	4.00%
Defined Benefit Plan, Expected Future Benefit Payments in Year One	5,200,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	5,900,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	5,800,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	6,900,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	6,800,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	38,300,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	38,400,000	39,500,000
Life insurance carried on plan participants [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	31,800,000	30,700,000
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 6,700,000	$ 7,300,000