Health Care Medical Claims Payable (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Health Care Medical Claims Payable Text Details [Line Items]
Difference in experience from assumptions, medical claims payable			$ (164)		$ (126)
Percent difference in experience from assumptions, medical claims payable			2.00%		1.50%
Difference in completion factors, medical claims payable			(76)		(87)
Percent difference in completion factors, medical claims payable			0.90%
Difference in medical cost trend, medical claims payable			(88)		(39)
Percent difference in medical cost trend, medical claims payable			1.10%
Schedule Of Medical Claims Payable Activity Details [Abstract]
Balance at January 1,			1,095	1,246	1,246
Less: Reinsurance and other amounts recoverable			194	236	236
Balance at January 1, net			901	1,010	1,010
Acquired HealthSpring balances, net			504		0
Incurred Claims Details [Abstract]
Current year			9,875		8,308
Prior years			(164)		(126)
Total incurred	3,269	2,014	9,711	6,125	8,182
Paid Claims Details [Abstract]
Current year			8,555		7,450
Prior years			1,166		841
Total paid			9,721		8,291
Ending Balance, net	1,395		1,395		901
Add: Reinsurance and other amounts recoverable	186		186		194
Medical claims payable	1,581		1,581		1,095
Schedule Of Medical Claims Payable Details [Abstract]
Incurred but not yet reported			1,372		952
Reported claims in process	132		132		129
Physician's Incentives and other medical expense payable	77		77		14
Medical claims payable	1,581		1,581		1,095
Pre Tax [Member]
Health Care Medical Claims Payable Text Details [Line Items]
Impact Of Prior Year Development On Shareholders Net Income			61
After Tax [Member]
Health Care Medical Claims Payable Text Details [Line Items]
Impact Of Prior Year Development On Shareholders Net Income			$ 52