Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Medical Premiums [Abstract]
Total premiums and fees																	$ 26,187		$ 18,966		$ 18,274
Mail order pharmacy revenues																	1,623		1,447		1,420
Other revenues																	121		244		254
Net investment income																	1,144		1,146		1,105
Total revenues	7,620		7,323		7,422		6,754		5,425		5,574		5,479		5,387		29,119		21,865		21,128
Depreciation and amortization																	560		345		292
Income taxes																	853		615		519
Segment earnings	406	[1]	466	[2]	380	[3]	371	[4]	273	[5]	183	[6]	391	[7]	413	[8]	1,623		1,260		1,279
Medicare Part D Fees																			61		57
Operating Segments [Member]
Medical Premiums [Abstract]
Segment earnings																	1,592		1,219		1,229
Global Health Benefits Segment [Member]
Medical Premiums [Abstract]
Guaranteed cost																	4,256	[9]	4,176	[9]	3,929	[9]
Experience-rated																	2,022	[10]	1,934	[10]	1,823	[10]
Stop loss																	1,672		1,451		1,287
International health care																	1,648		1,344		976
Dental																	1,005		894		804
Medicare																	4,969		489		1,470
Medicaid																	207		0		0
Medicare Part D																	1,421		685		615
Other																	677		600		543
Total medical																	17,877		11,573		11,447
Fees																	3,096	[11]	2,870	[11]	2,687	[11]
Total premiums and fees																	20,973		14,443		14,134
Mail order pharmacy revenues																	1,623		1,447		1,420
Other revenues																	225		236		269
Net investment income																	259		263		230
Total revenues																	23,080		16,389		16,053
Depreciation and amortization																	500		297		255
Income taxes																	793		616		520
Segment earnings																	1,418		1,105		940
Commercial Operating Segment [Member]
Medical Premiums [Abstract]
Number of states in which products and services are offered	50																50
Medicare Advantage Plans [Member]
Medical Premiums [Abstract]
Number of states in which products and services are offered	13																13
Medicare Part D Plans [Member]
Medical Premiums [Abstract]
Number of states in which products and services are offered	50																50
Group Disability And Life Segment [Member]
Medical Premiums [Abstract]
Total premiums and fees																	3,109		2,857		2,770
Other revenues																	0		0		123
Net investment income																	300		291		287
Total revenues																	3,409		3,148		3,180
Depreciation and amortization																	10		10		8
Income taxes																	116		113		127
Segment earnings																	279		295		305
Group Disability And Life Segment [Member] | Life [Member]
Medical Premiums [Abstract]
Total premiums and fees																	1,426		1,333		1,341
Group Disability And Life Segment [Member] | Disability [Member]
Medical Premiums [Abstract]
Total premiums and fees																	1,413		1,268		1,167
Group Disability And Life Segment [Member] | Other [Member]
Medical Premiums [Abstract]
Total premiums and fees																	270		256		262
Global Supplemental Benefits Segment [Member]
Medical Premiums [Abstract]
Total premiums and fees																	1,984		1,528		1,231
Other revenues																	21		15		22
Net investment income																	90		83		69
Total revenues																	2,095		1,626		1,322
Depreciation and amortization																	28		13		8
Income taxes																	36		36		42
Equity in income of investees																	10		15		18
Segment earnings																	142		97		84
Corporate Segment [Member]
Medical Premiums [Abstract]
Other revenues																	(61)		(58)		(62)
Net investment income																	5		6		1
Total revenues																	(56)		(52)		(61)
Depreciation and amortization																	0		0		0
Income taxes																	(148)		(101)		(98)
Segment earnings																	$ (329)		$ (184)		$ (211)

[1] The fourth quarter of 2012 includes an after-tax gain of $7 million for the GMIB business and an after-tax charge of $68 million for litigation matters

[2] The third quarter of 2012 includes an after-tax gain of $32 million for the GMIB business, an after-tax charge of $12 million for costs associated with acquisitions, and an after-tax charge of $50 million for costs associated with a realignment and efficiency plan.

[3] The second quarter of 2012 includes an after-tax loss of $51 million for the GMIB business.

[4] The first quarter of 2012 includes an after-tax gain of $41 million for the GMIB business, an after-tax charge of $28 million for costs associated with acquisitions, and an after-tax charge of $13 million for costs associated a litigation matter in Global Health Care.

[5] The fourth quarter of 2011 includes an after-tax gain of $7 million for the GMIB business and, an after-tax charge of $31 million for costs associated with acquisitions.

[6] The third quarter of 2011 includes an after-tax loss of $134 million for the GMIB business.

[7] The second quarter of 2011 includes an after-tax loss of $21 million for the GMIB business.

[8] The first quarter of 2011 includes an after-tax gain of $13 million for the GMIB business and a net tax benefit of $24 million related to the resolution of a Federal tax matter.

[9] Excludes the international health care business.

[10] Includes minimum premium business that has a risk profile similar to experience-rated funding arrangements. The risk portion of minimum premium revenue is reported in experience-rated medical premium whereas the self funding portion of minimum premium revenue is reported in fees. Also includes certain non-participating cases for which special customer level reporting of experience is required.

[11] Includes fees related to the international health care business. Fees related to Medicare Part D of $61 million in 2011 and $57 million in 2010 have been reclassified to premiums to conform to current presentation.