Segments of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues by significant business segment and sub-segment
Total premiums earned	$ 848	$ 835	$ 2,091	$ 2,043
Investment income	327	310	981	916
Life, accident and health premiums	80	107	290	324
Realized gains (losses) on securities	85	8	145	27
Realized gains (losses) on subsidiaries	156		155	(3)
Other income	49	47	135	136
Total revenues	1,563	1,335	3,826	3,467
Property and Casualty Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	69	73	210	223
Realized gains	44	15	88	47
Other income	16	20	47	55
Total revenues	977	943	2,436	2,368
Annuity and Supplemental Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	270	236	789	694
Life, accident and health premiums	80	107	290	324
Realized gains (losses) on securities	41	(8)	57	(22)
Realized gains (losses) on subsidiaries	156		155	(2)
Other income	30	27	84	79
Total revenues	577	362	1,375	1,073
Other Segment [Member]
Revenues by significant business segment and sub-segment
Total revenues	9	30	15	26
Specialty Property and transportation [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	487	500	1,040	1,029
Specialty casualty [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	243	216	699	651
Specialty financial [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	100	101	301	313
Specialty Other [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	$ 18	$ 18	$ 51	$ 50