Segments of Operations (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues by significant business segment and sub-segment
Total premiums earned	$ 609	$ 572	$ 1,208	$ 1,151
Investment income	306	294	606	589
Life, accident and health premiums	107	113	217	228
Realized gains (losses)	19	11	16	15
Other income	48	54	89	98
Total revenues	1,093	1,052	2,132	2,086
Specialty Property and Transportation [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	274	209	529	425
Specialty Casualty [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	219	219	435	437
Specialty Financial [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	100	127	212	255
Specialty Other [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	16	17	32	34
Property and Casualty Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	75	85	148	177
Realized gains (losses)	32	13	32	23
Other income	20	21	35	36
Total revenues	736	691	1,423	1,387
Annuity and Supplemental Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	230	208	456	410
Life, accident and health premiums	107	113	217	228
Realized gains (losses)	(13)	(2)	(16)	(8)
Other income	27	33	50	58
Total revenues	351	352	707	688
Other Segment [Member]
Revenues by significant business segment and sub-segment
Total revenues	$ 6	$ 9	$ 2	$ 11