Basis of Presentation Basis of Presentation (Details) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Aarp Program [Member]	Dec. 31, 2010 Aarp Program [Member]	Dec. 31, 2009 Aarp Program [Member]	Dec. 31, 2012 Medicare Part D Initial coverage limit [Member]	Dec. 31, 2011 Medicare Part D Initial coverage limit [Member]	Dec. 31, 2011 reinsurance receivable current [Member]	Dec. 31, 2010 reinsurance receivable current [Member]	Dec. 31, 2011 reinsurance receivalbe non-current [Member]	Dec. 31, 2010 reinsurance receivalbe non-current [Member]	Dec. 31, 2012 Medicare Part D catastrophic coverage [Member]	Dec. 31, 2011 Medicare Part D catastrophic coverage [Member]	Dec. 31, 2012 Medicare Part D annual out of pocket maximum [Member]	Dec. 31, 2011 Medicare Part D annual out of pocket maximum [Member]
Checks Outstanding In Excess Of Bank Deposits	$ 1,500,000,000	$ 1,300,000,000
Interest Income And Realized Gains Losses Related To Assets Under Management			99,000,000	107,000,000	99,000,000
CMS obligation to pay costs incurred by individual members	80.00%
Mandated Discounts On Brand Name Prescription Drugs Under Medicare Part D Program	50.00%
Variance Of Risk Share	5.00%
Medicare Part D Initial Coverage Limit						2,930	2,840
Medicare Part D catastrophic coverage												6,658	6,448
Medicare Part D annual out of pocket maximum														4,700	4,550
Rate Stabilization Fund	1,300,000,000	1,300,000,000
Reinsurance Recoverables	1,900,000,000	2,000,000,000
Other current receivables, net	2,255,000,000	1,643,000,000						125,000,000	126,000,000
Other assets	$ 2,088,000,000	$ 2,108,000,000								$ 1,800,000,000	$ 1,900,000,000
Number Of Days Notice Required To Cancel Health Insurance Contract	30 days