Health Care Medical Claims Payable (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Health Care Medical Claims Payable Text Details [Abstract]
Difference in experience from assumptions, medical claims payable	$ (135)		$ (126)
Percent difference in experience from assumptions, medical claims payable	1.60%		1.50%
Difference in completion factors, medical claims payable	(60)		(87)
Percent difference in completion factors, medical claims payable	0.70%		1.00%
Difference in medical cost trend, medical claims payable	(75)		(39)
Percent difference in medical cost trend, medical claims payable	0.90%		0.50%
After Tax Impact Of Prior Year Development On Shareholders Net Income	38	22
Schedule Of Medical Claims Payable Activity Details [Abstract]
Balance at January 1,	1,095	1,246	1,246
Less: Reinsurance and other amounts recoverable	202		194	236
Balance at January 1, net	1,496		901	1,010
Acquired HealthSpring balances, net	510		0
Incurred Claims Details [Abstract]
Current year	3,172		8,308
Prior years	(135)		(126)
Total incurred	3,037	2,077	8,182
Paid Claims Details [Abstract]
Current year	2,002		7,450
Prior years	950		841
Total paid	2,952		8,291
Ending Balance, net	1,496		901	1,010
Add: Reinsurance and other amounts recoverable	202		194	236
Medical claims payable	1,698		1,095	1,246
Schedule Of Medical Claims Payable Details [Abstract]
Incurred but not yet reported	1,416		952
Reported claims in process	170		129
Physician's Incentives and other medical expense payable	112		14
Medical claims payable	$ 1,698		$ 1,095	$ 1,246