Segments of Operations (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenues by significant business segment and sub-segment
Total premiums earned	$ 835	$ 736	$ 2,043	$ 1,887
Investment income	310	296	916	885
Life, accident and health premiums	107	112	324	340
Realized gains (losses)	8	35	24	50
Other income	47	57	136	155
Total revenues	1,335	1,255	3,467	3,341
Specialty Property and Transportation [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	500	407	1,029	832
Specialty Casualty [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	216	224	651	661
Specialty Financial [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	101	92	313	347
Specialty Other [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	18	13	50	47
Property and Casualty Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	73	80	221	257
Realized gains (losses)	15	46	47	69
Other income	20	13	55	49
Total revenues	943	875	2,366	2,262
Annuity and Supplemental Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	236	215	692	625
Life, accident and health premiums	107	112	324	340
Realized gains (losses)	(8)	(11)	(24)	(19)
Other income	28	23	78	81
Total revenues	363	339	1,070	1,027
Other Segment [Member]
Revenues by significant business segment and sub-segment
Total revenues	$ 29	$ 41	$ 31	$ 52