Segments of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues by significant business segment and sub-segment
Total premiums earned	$ 603	$ 599
Investment income	322	300
Life, accident and health premiums	105	110
Realized gains (losses)	44	(3)
Other income	39	41
Total revenues	1,113	1,039
Property and Casualty Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	71	75
Realized gains (losses)	31
Other income	13	15
Total revenues	718	689
Annuity and Supplemental Insurance [Member]
Revenues by significant business segment and sub-segment
Investment income	252	228
Life, accident and health premiums	105	110
Realized gains (losses)	13	(3)
Other income	26	24
Total revenues	396	359
Other Segment [Member]
Revenues by significant business segment and sub-segment
Total revenues	(1)	(9)
Specialty Property and Transportation [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	263	255
Specialty Casualty [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	220	216
Specialty Financial [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	103	112
Specialty Other [Member]
Revenues by significant business segment and sub-segment
Total premiums earned	$ 17	$ 16