Segments of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues by significant business segment and sub-segment
Total premiums earned	$ 640	$ 609	$ 1,243	$ 1,208
Investment income	332	306	654	606
Life, accident and health premiums	105	107	210	217
Other income	47	48	86	89
Total revenues	1,150	1,093	2,263	2,132
Property and Casualty Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	70	75	141	150
Realized gains (losses)	13	32	44	32
Other income	18	20	31	35
Total revenues	741	736	1,459	1,425
Annuity and Supplemental Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	267	230	519	458
Life, accident and health premiums	105	107	210	217
Realized gains (losses)	2	(13)	15	(16)
Other income	28	28	54	52
Total revenues	402	352	798	711
Other Segment [Member]
Revenues by significant business segment and sub-segment
Total revenues	7	5	6	(4)
Specialty Property and Transportation [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	290	274	553	529
Specialty Casualty [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	236	219	456	435
Specialty Financial [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	98	100	201	212
Specialty Other [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	$ 16	$ 16	$ 33	$ 32