Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	$ 8,374	$ 7,665	$ 16,551	$ 15,422
Segment earnings (loss)	530	488	1,031	452
Realized investment gains, net of taxes	43	17	70	110
Shareholders' Net Income	573	505	1,101	562
Operating Segments [Member] | Global Health Benefits Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	6,726	6,171	13,272	12,468
Segment earnings (loss)	402	379	841	806
Operating Segments [Member] | Global Supplemental Benefits Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	729	622	1,419	1,234
Segment earnings (loss)	61	49	114	104
Operating Segments [Member] | Group Disability And Life Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	891	847	1,806	1,705
Segment earnings (loss)	110	104	177	102
Operating Segments [Member] | Other Operations Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	30	30	60	23
Segment earnings (loss)	13	15	30	(447)
Corporate [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and Other revenues	(2)	(5)	(6)	(8)
Segment earnings (loss)	$ (56)	$ (59)	$ (131)	$ (113)