Segment Information (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 4,576	$ 4,728
Net investment income:
Securities available-for-sale and other	1,070	1,108
Equity securities, trading	2,866	803
Total net investment income	3,936	1,911
Net realized capital losses	(910)	(403)
Other revenues	59	64
Total revenues	7,661	6,300
Property & Casualty Commercial [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	1,557	1,498
Workers' Compensation [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	733	665
Property [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	125	135
Automobiles [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	146	146
Package Business [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	292	283
Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	141	135
Fidelity and Surety [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	52	55
Professional Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	68	79
Group Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	972	1,044
Group Disability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	443	477
Group life and accident [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	479	517
Other [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	50	50
Consumer Markets [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	909	956
Automobiles [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	632	672
Homeowners [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	277	284
Individual Annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	368	440
Variable Annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	349	436
Fixed / MVA and other annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	19	4
Individual Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	227	209
Variable Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	87	90
Universal Life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	126	106
Term / other life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	14	13
Retirement Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	96	97
401(k) [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	84	84
Government Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	12	13
Mutual Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	151	178
Non-proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	136	162
Proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	15	16
Life Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	244	254
Property & Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	0	0
Corporate [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 52	$ 52