Segment Information (Details 1) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues by Product Line
Earned premiums, fees and other considerations	$ 4,764	$ 4,692	$ 9,492	$ 9,399
Net investment income (loss):
Securities available-for-sale and other	1,104	1,148	2,212	2,202
Equity securities, trading	(597)	(2,649)	206	(1,948)
Total net investment income (loss)	507	(1,501)	2,418	254
Net realized capital gains (losses)	69	9	(334)	(265)
Other revenues	61	65	125	129
Total revenues	5,401	3,265	11,701	9,517
Property & Casualty Commercial [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	1,517	1,415	3,015	2,839
Workers' Compensation [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	685	573	1,350	1,148
Property [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	134	137	269	277
Automobiles Commercial [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	145	151	291	303
Package Business [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	285	282	568	561
Liability [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	134	135	269	274
Fidelity and Surety [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	54	57	109	113
Professional Liability [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	80	80	159	163
Group Benefits [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	1,076	1,074	2,120	2,176
Group disability [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	516	502	993	1,033
Group life and accident [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	511	514	1,028	1,026
Other Group Benefit [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	49	58	99	117
Consumer Markets [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	939	995	1,895	1,991
Automobiles Consumer [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	657	711	1,329	1,424
Homeowners [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	282	284	566	567
Global Annuity [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	645	643	1,295	1,268
Variable Global Annuity [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	631	628	1,270	1,228
Fixed / MVA and other annuity [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	17	11	27	23
Institutional investment products [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	(3)	4	(2)	17
Life Insurance [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	257	259	510	519
Variable Life Insurance [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	91	101	182	203
Universal Life Insurance [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	109	104	215	209
Term / other life [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	12	11	24	24
PPLI [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	45	43	89	83
Retirement Plans [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	101	89	198	176
401(k) [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	88	80	172	156
Government plans [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	13	9	26	20
Mutual Funds [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	175	167	353	334
Non-proprietary [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	161	152	323	303
Proprietary [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	14	15	30	31
Corporate and Other [Member]
Revenues by Product Line
Earned premiums, fees and other considerations	$ 54	$ 50	$ 106	$ 96