Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Allowance for doubtful accounts netted against premiums, accounts and notes receivable	$ 51,000,000	$ 45,000,000
Allowance for doubtful accounts netted against reinsurance recoverables	4,000,000	5,000,000
Amortization for policy acquisition costs recorded in other operating expense	218,000,000	259,000,000	251,000,000
Statement Line Items [Line Items]
Goodwill	6,001,000,000	3,164,000,000	3,119,000,000
Finite Lived Intangible Assets Amortization Method	accelerated or straight-line basis
Finite Lived Intangible Assets Useful Life Minimum	1
Finite Lived Intangible Assets Useful Life Maximum	30
Future policy benefits interest rate assumptions range low	1.00%
Future policy benefits interest rate assumptions range high	10.00%
Discount rate assumption for LTD and Workers' comp claim liabilities range low	1.83%
Discount rate assumption for LTD and Workers' comp claim liabilities range high	6.25%
Discounted liability for long-term disability and workers' compensation business	3,200,000,000	3,200,000,000
Percent of Administrative Service Only fees at risk for performance guarantees	16.00%
Percent of ASO fees reimbursed for performance guarantees	1.00%
Percent of total life insurance in force that is participating business	1.00%
Global Health Benefits Segment [Member]
Statement Line Items [Line Items]
Goodwill	5,700,000,000
Global Supplemental Benefits Segment [Member]
Statement Line Items [Line Items]
Goodwill	$ 350,000,000
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
Internal-use software [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
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