Segment Information (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 4,514	$ 4,764	$ 9,090	$ 9,492
Net investment income:
Securities available-for-sale and other	1,097	1,104	2,167	2,212
Equity securities, trading	(1,687)	(597)	1,179	206
Total net investment income (loss)	(590)	507	3,346	2,418
Net realized capital gains (losses)	589	69	(321)	(334)
Other revenues	61	61	120	125
Total revenues	4,574	5,401	12,235	11,701
Property & Casualty Commercial [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	1,552	1,517	3,109	3,015
Workers' Compensation [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	737	685	1,470	1,350
Property [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	126	134	251	269
Automobiles [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	146	145	292	291
Package Business [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	289	285	581	568
Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	136	134	277	269
Fidelity and Surety [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	51	54	103	109
Professional Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	67	80	135	159
Group Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	966	1,076	1,938	2,120
Group Disability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	439	516	882	993
Group life and accident [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	478	511	957	1,028
Other [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	49	49	99	99
Consumer Markets [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	904	939	1,813	1,895
Automobiles [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	630	657	1,262	1,329
Homeowners [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	274	282	551	566
Individual Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	220	212	447	421
Variable Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	85	91	172	182
Universal Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	122	109	248	215
Term / other life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	13	12	27	24
Retirement Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	94	101	190	198
401(k) [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	81	88	165	172
Government Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	13	13	25	26
Mutual Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	148	175	299	353
Non-proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	134	161	270	323
Proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	14	14	29	30
Life Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	587	690	1,199	1,384
Property and Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	(2)	0	(2)	0
Corporate [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 45	$ 54	$ 97	$ 106