Segments Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues of the P&C Group by geographic area [Abstract]
Revenues	$ 3,345	$ 3,420	$ 3,400	$ 3,420	$ 3,411	$ 3,267	$ 3,318	$ 3,323	$ 13,585	$ 13,319	$ 13,016
Property and casualty insurance [Member]
Revenues of the P&C Group by geographic area [Abstract]
Revenues									13,242	12,805	12,918
Property and casualty insurance [Member] | United States [Member]
Revenues of the P&C Group by geographic area [Abstract]
Revenues									9,729	9,642	9,991
Property and casualty insurance [Member] | International [Member]
Revenues of the P&C Group by geographic area [Abstract]
Revenues									$ 3,513	$ 3,163	$ 2,927