Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended															12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Medical Premiums [Abstract]
Total premiums and fees																$ 28,976		$ 26,187		$ 18,966
Mail order pharmacy revenues																1,827		1,623		1,447
Other revenues																200		121		244
Net investment income																1,164		1,144		1,146
Total revenues	8,151		8,066	7,980		8,183		7,620		7,323		7,422		6,754		32,380		29,119		21,865
Depreciation and amortization																597		560		345
Income taxes																698		853		615
Segment earnings	361	[1]	553	505	[2]	57	[3]	406	[4]	466	[5]	380	[6]	371	[7]	1,476		1,623		1,260
Operating Segments [Member]
Medical Premiums [Abstract]
Segment earnings																1,335		1,592		1,219
Global Health Care [Member]
Medical Premiums [Abstract]
Guaranteed cost																4,463	[8]	4,256	[8]	4,176	[8]
Experience-rated																2,292	[9]	2,022	[9]	1,934	[9]
Stop loss																1,907		1,672		1,451
International health care																1,752		1,648		1,344
Dental																1,139		1,005		894
Medicare																5,639		4,969		489
Medicaid																317		207		0
Medicare Part D																1,387		1,421		685
Other																730		677		600
Total medical																19,626		17,877		11,573
Fees																3,307	[10]	3,096	[10]	2,870	[10]
Total premiums and fees																22,933		20,973		14,443
Mail order pharmacy revenues																1,827		1,623		1,447
Other revenues																211		225		236
Net investment income																325		259		263
Total revenues																25,296		23,080		16,389
Depreciation and amortization																529		516		314
Income taxes																822		793		616
Segment earnings																1,517		1,418		1,105
Global Supplemental Benefits [Member]
Medical Premiums [Abstract]
Total premiums and fees																2,513		1,984		1,528
Other revenues																26		21		15
Net investment income																100		90		83
Total revenues																2,639		2,095		1,626
Depreciation and amortization																50		29		14
Income taxes																50		36		36
Equity in income of investees																17		10		15
Segment earnings																175		142		97
Group Disability And Life [Member]
Medical Premiums [Abstract]
Total premiums and fees																3,425		3,109		2,857
Other revenues																1		0		0
Net investment income																321		300		291
Total revenues																3,747		3,409		3,148
Depreciation and amortization																14		11		11
Income taxes																101		116		113
Segment earnings																259		279		295
Group Disability And Life [Member] | Life [Member]
Medical Premiums [Abstract]
Total premiums and fees																1,552		1,426		1,333
Group Disability And Life [Member] | Disability [Member]
Medical Premiums [Abstract]
Total premiums and fees																1,616		1,413		1,268
Group Disability And Life [Member] | Other [Member]
Medical Premiums [Abstract]
Total premiums and fees																257		270		256
Corporate [Member]
Medical Premiums [Abstract]
Other revenues																(47)		(61)		(58)
Net investment income																10		5		6
Total revenues																(37)		(56)		(52)
Depreciation and amortization																3		3		4
Income taxes																(110)		(148)		(101)
Segment earnings																$ (222)		$ (329)		$ (184)

[1] The fourth quarter of 2013 includes an after-tax charge of $40 million for an organizational efficiency plan.

[2] The second quarter of 2013 includes an after-tax charge of $24 million for the Pharmacy Benefits Manager (“PBM”) partnering agreement with Catamaran.

[3] The first quarter of 2013 includes an after-tax gain of $25 for the GMIB business, an after-tax charge of $507 million for the transaction with Berkshire to effectively exit the Run-off Reinsurance business, and an after-tax charge of $51 million related to the disability claims regulatory matter in the Group Disability and Life segment.

[4] 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.

[5] 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 an organizational efficiency plan.

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

[7] 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.

[8] Excludes the international health care business.

[9] 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.

[10] 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.