Schedule III - Supplementary Insurance Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	$ 1,502		$ 1,395		$ 1,198
Future policy benefits and contractholder deposit funds	18,072		17,776		17,773
Medical claims payable and unpaid claims	6,580		6,348		5,918
Unearned premiums	621		580		549
Premiums	27,214	[1]	25,575	[1]	23,017	[1]
Net investment income	1,166	[2]	1,164	[2]	1,144	[2]
Benefit expenses	21,334	[1],[3]	20,865	[1],[3]	17,900	[1],[3]
Amortization of deferred policy acquisition expenses	289		255		218
Other operating expenses	9,987	[4]	9,084	[4]	8,524	[4]
Corporate [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	0		0		0
Future policy benefits and contractholder deposit funds	0		0		0
Medical claims payable and unpaid claims	(5)		(6)		(21)
Unearned premiums	0		0		0
Premiums	0	[1]	0	[1]	0	[1]
Net investment income	1	[2]	10	[2]	5	[2]
Benefit expenses	0	[1],[3]	0	[1],[3]	0	[1],[3]
Amortization of deferred policy acquisition expenses	0		0		0
Other operating expenses	340	[4]	328	[4]	458	[4]
Global Health Care [Member] | Operating Segments [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	17		20		19
Future policy benefits and contractholder deposit funds	182		197		175
Medical claims payable and unpaid claims	2,180		2,050		1,856
Unearned premiums	155		116		111
Premiums	20,709	[1]	19,626	[1]	17,877	[1]
Net investment income	337	[2]	325	[2]	259	[2]
Benefit expenses	16,694	[1],[3]	15,867	[1],[3]	14,228	[1],[3]
Amortization of deferred policy acquisition expenses	73		69		68
Other operating expenses	7,843	[4]	7,021	[4]	6,573	[4]
Global Supplemental Benefits [Member] | Operating Segments [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	1,437		1,323		1,113
Future policy benefits and contractholder deposit funds	2,785		2,525		2,227
Medical claims payable and unpaid claims	339		305		306
Unearned premiums	431		419		388
Premiums	2,844	[1]	2,496	[1]	1,975	[1]
Net investment income	109	[2]	100	[2]	90	[2]
Benefit expenses	1,544	[1],[3]	1,310	[1],[3]	1,005	[1],[3]
Amortization of deferred policy acquisition expenses	209		178		141
Other operating expenses	981	[4]	924	[4]	770	[4]
Group Disability And Life [Member] | Operating Segments [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	1		1		1
Future policy benefits and contractholder deposit funds	1,662		1,615		1,599
Medical claims payable and unpaid claims	3,844		3,739		3,482
Unearned premiums	15		23		26
Premiums	3,549	[1]	3,348	[1]	3,044	[1]
Net investment income	335	[2]	321	[2]	300	[2]
Benefit expenses	2,716	[1],[3]	2,621	[1],[3]	2,290	[1],[3]
Amortization of deferred policy acquisition expenses	1		1		3
Other operating expenses	796	[4]	765	[4]	721	[4]
Other Operations [Member] | Operating Segments [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	47		51		65
Future policy benefits and contractholder deposit funds	13,443		13,439		13,772
Medical claims payable and unpaid claims	222		260		295
Unearned premiums	20		22		24
Premiums	112	[1]	105	[1]	121	[1]
Net investment income	384	[2]	408	[2]	490	[2]
Benefit expenses	380	[1],[3]	1,067	[1],[3]	377	[1],[3]
Amortization of deferred policy acquisition expenses	6		7		6
Other operating expenses	$ 27	[4]	$ 46	[4]	$ 2	[4]

[1] Amounts presented are shown net of the effects of reinsurance. See Note 7 to the Consolidated Financial Statements included in this Form 10-K.

[2] The allocation of net investment income is based upon the investment year method, the identification of certain portfolios with specific segments, or a combination of both.

[3] Benefit expenses include Global Health Care medical claims expense and other benefit expenses.

[4] Other operating expenses include mail order pharmacy costs and other operating expenses, and excludes amortization of deferred policy acquisition expenses.