Acquisitions and Dispositions (Details) (USD $)	12 Months Ended	36 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	1 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Nov. 09, 2012	Dec. 31, 2014	Aug. 31, 2012	Jan. 31, 2012 States
Business Acquisition [Line Items]
Number of significant transactions completed	3
Pro forma revenues
Pro forma net income
Other acquisitions and dispositions, results
Finans Emeklilik [Member]
Business Acquisition [Line Items]
Acquisition effective date			Nov. 09, 2012
Name Of Acquired Entity				Finans Emeklilik ve Hayat A.S.
Percentage Of Voting Interests Acquired			51.00%
Ownership Percentage Retained by Noncontrolling Owners			49.00%
Description Of Acquired Entity				Finans Emeklilik operates in life insurance, accident insurance and pension product markets.
Minority Interest Redemption Term			15 years
Cash paid to acquire business			116,000,000
Great American Supplemental Benefits Group [Member]
Business Acquisition [Line Items]
Acquisition effective date					Aug. 31, 2012
Name Of Acquired Entity				Great American Supplemental Benefits Group
Description Of Acquired Entity				one of the largest providers of supplemental health insurance products in the U.S.
Cash paid to acquire business					326,000,000
HealthSpring [Member]
Business Acquisition [Line Items]
Acquisition effective date						Jan. 31, 2012
Name Of Acquired Entity				HealthSpring, Inc.
Description Of Acquired Entity				At the time of acquisition, HealthSpring provided Medicare Advantage coverage in 15 states and the District of Columbia, as well as a large, national stand-alone Medicare prescription drug business.
Healthspring Medicare Advantage Coverage Number Of States						15
Price per share						$ 55
Total merger consideration						3,800,000,000
Acquisition-related costs	53,000,000
Acquisitions-related costs, after-tax	40,000,000
HealthSpring [Member] | Operating Segments [Member]
Business Acquisition [Line Items]
Acquisitions-related costs, after-tax	7,000,000
HealthSpring [Member] | Corporate [Member]
Business Acquisition [Line Items]
Acquisitions-related costs, after-tax	$ 33,000,000