Schedule III - Supplementary Insurance Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	$ 1,198	$ 817	$ 701
Future policy benefits and contractholder deposit funds	17,773	17,146	16,656
Medical claims payable and unpaid claims	5,918	5,241	5,263
Unearned premiums and fees	549	502	416
Premiums and fees	26,187	18,966	18,274
Net investment income	1,144	1,146	1,105
Benefit expenses	17,900	12,490	12,233
Amortization of deferred policy acquisition expenses	218	259	251
Other operating expenses	8,524	7,240	6,842
Global Health Benefits Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	19	19	22
Future policy benefits and contractholder deposit funds	175	170	178
Medical claims payable and unpaid claims	1,856	1,443	1,555
Unearned premiums and fees	111	103	87
Premiums and fees	20,973	14,443	14,134
Net investment income	259	263	230
Benefit expenses	14,228	9,125	9,222
Amortization of deferred policy acquisition expenses	68	139	155
Other operating expenses	6,573	5,404	5,216
Global Supplemental Benefits Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	1,113	729	609
Future policy benefits and contractholder deposit funds	2,227	1,255	1,085
Medical claims payable and unpaid claims	306	177	112
Unearned premiums and fees	388	346	271
Premiums and fees	1,984	1,528	1,231
Net investment income	90	83	69
Benefit expenses	1,005	754	603
Amortization of deferred policy acquisition expenses	141	110	84
Other operating expenses	770	628	505
Group Disability And Life Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	1	1	2
Future policy benefits and contractholder deposit funds	1,599	1,572	1,464
Medical claims payable and unpaid claims	3,482	3,228	3,201
Unearned premiums and fees	26	26	27
Premiums and fees	3,109	2,857	2,770
Net investment income	300	291	287
Benefit expenses	2,290	2,086	2,035
Amortization of deferred policy acquisition expenses	3	4	6
Other operating expenses	721	650	707
Run Off Reinsurance Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	0	0	0
Future policy benefits and contractholder deposit funds	1,094	1,172	1,139
Medical claims payable and unpaid claims	153	240	244
Unearned premiums and fees	0	0	0
Premiums and fees	21	24	25
Net investment income	102	103	114
Benefit expenses	16	140	(22)
Amortization of deferred policy acquisition expenses	0	0	0
Other operating expenses	(12)	265	113
Other Operations Segment [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	65	68	68
Future policy benefits and contractholder deposit funds	12,678	12,977	12,790
Medical claims payable and unpaid claims	142	160	159
Unearned premiums and fees	24	27	31
Premiums and fees	100	114	114
Net investment income	388	400	404
Benefit expenses	361	385	395
Amortization of deferred policy acquisition expenses	6	6	6
Other operating expenses	51	60	53
Corporate Segment [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	(21)	(7)	(8)
Unearned premiums and fees	0	0	0
Premiums and fees	0	0	0
Net investment income	5	6	1
Benefit expenses	0	0	0
Amortization of deferred policy acquisition expenses	0	0	0
Other operating expenses	$ 421	$ 233	$ 248