Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	$ 8,442	$ 7,742	$ 24,993	$ 23,164
Segment earnings (loss)	519	536	1,550	988
Realized investment gains, net of taxes	15	17	85	127
Shareholders' Net Income	534	553	1,635	1,115
Operating Segments [Member] | Global Health Benefits Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	6,757	6,230	20,029	18,698
Segment earnings (loss)	434	424	1,275	1,230
Operating Segments [Member] | Global Supplemental Benefits Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	747	638	2,166	1,872
Segment earnings (loss)	83	39	197	143
Operating Segments [Member] | Group Disability And Life Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	910	848	2,716	2,553
Segment earnings (loss)	55	92	232	194
Operating Segments [Member] | Other Operations Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	35	29	95	52
Segment earnings (loss)	19	35	49	(412)
Corporate [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	(7)	(3)	(13)	(11)
Segment earnings (loss)	$ (72)	$ (54)	$ (203)	$ (167)