Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Significant Accounting Policies Text Details [Abstract]
Cumulative effect of adoption of OTTI guidance			$ 18,000,000
Allowance for doubtful accounts neted against premiums, accounts and notes receivable	45,000,000	49,000,000
Allowance for doubtful accounts neted against reinsurance recoverables	5,000,000	10,000,000
Amortization for policy acquisition costs recorded in other operating expense	334,000,000	312,000,000	299,000,000
Finite Lived Intangible Assets Useful Life Minimum	1
Finite Lived Intangible Assets Useful Life Maximum	30
Finite Lived Intangible Assets Amortization Method	acclerated or straight-line
Future policy benefits interest rate assumptions range low	1.00%
Future policy benefits interest rate assumptions range high	10.00%
Discount rate assumption for investments supporting LTD and Workers' comp claim liabilities range low	3.80%
Discount rate assumption for investments supporting LTD and Workers' comp claim liabilities range high	6.25%
Discounted liability for long-term disability and workers' compensation business	3,200,000,000	3,100,000,000
Percentage of total life insurance in force that is participating business	1.00%
Rehabilitation period minimum for foreclosed properties	3
Rehabilitation Period in Years Maximum For Foreclosed Properties	5
Impact of implementing new accounting guidance for deferred acquisition costs - lower range	250,000,000
Segment Reporting Goodwill [Line Items]
Goodwill	3,164,000,000	3,119,000,000
Impact of implementing new accounting guidance for deferred acquisition costs - upper range	300,000,000
Estimated Deferred Acquisition Costs No Longer Eligible for Deferral In 2012	$ 70,000,000
Building And Building Improvements Member
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life Minimum	10
Property Plant And Equipment Useful Life Maximum	40
Furniture and equipment (including computer equipment)
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life Minimum	3
Property Plant And Equipment Useful Life Maximum	10
Internal-use software reported in property and equipment [Member]
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life Minimum	1
Property Plant And Equipment Useful Life Maximum	5
Internally developed software
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life Minimum	3
Property Plant And Equipment Useful Life Maximum	7