Segments of Operations (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating earnings before income taxes by significant business segment and sub-segment
Realized gains (losses)	$ 73	$ 88	$ 38
Operating earnings before income taxes	560	689	812
Property and Casualty Insurance [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	180	296	417
Investment and other income, net	263	299	338
Realized gains (losses)	97	88	123
Operating earnings before income taxes	540	683	878
Annuity and Supplemental Insurance [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Operations	224	202	162
Realized gains (losses)	(23)		(86)
Operating earnings before income taxes	201	202	76
Other Segment [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Operating earnings before income taxes	(181)	(196)	(142)
Specialty Property and Transportation [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	113	140	236
Specialty Casualty [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	39	47	63
Specialty Financial [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	61	112	134
Specialty Other [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	18	9	(9)
Other Lines [Member]
Operating earnings before income taxes by significant business segment and sub-segment
Property and casualty insurance underwriting income (loss)	$ (51)	$ (12)	$ (7)