Segment Information (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Member co-share amounts and government subsidies			$ 4,200,000,000	$ 3,500,000,000	$ 3,500,000,000
Percentage of total premium and services revenues derived from contracts with the federal government			76.00%	76.00%	73.00%
Prior year favorable reserve releases			205,000,000	231,000,000
Write-down of deferred acquisition costs		147,000,000		147,000,000
Charge related to closed block of long-term care policies	139,000,000			139,000,000
Retail [Member]
Segment Reporting Information [Line Items]
Prior year favorable reserve releases			147,000,000	198,000,000
Write-down of deferred acquisition costs				147,000,000
Employer Group [Member]
Segment Reporting Information [Line Items]
Prior year favorable reserve releases			52,000,000	33,000,000
Other Businesses [Member]
Segment Reporting Information [Line Items]
Charge related to closed block of long-term care policies				$ 139,000,000