Segment Information - Summarized Financial Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	$ 7,757	$ 6,453
Realized investment gains (losses) from continuing operations, net of taxes and noncontrolling interest	93	12
Shareholders' net income	57	371
Operating Segments [Member]
Segment Reporting Information [Line Items]
Shareholders' net income	(36)	359
Global Heath Care Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	6,297	5,306
Shareholders' net income	427	276
Global Supplemental Benefits Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	612	452
Shareholders' net income	55	43
Group Disability And Life Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	858	763
Shareholders' net income	(2)	68
Run Off Reinsurance Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	(37)	(90)
Shareholders' net income	(483)	30
Other Operations Segment [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	38	39
Shareholders' net income	21	20
Corporate [Member]
Segment Reporting Information [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	(11)	(17)
Shareholders' net income	(54)	(78)
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Realized investment gains (losses) from continuing operations, net of taxes and noncontrolling interest	$ 93	$ 12