Segments Information - Revenues of Property and Casualty Group by Geographic Area (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues by geographic area
Revenues	$ 3,476	$ 3,403	$ 3,551	$ 3,517	$ 3,400	$ 3,362	$ 3,423	$ 3,410	$ 13,947	$ 13,595	$ 13,585
P&C Group [Member]
Revenues by geographic area
Revenues									13,502	13,356	13,242
P&C Group [Member] | Reportable Geographical Components [Member] | United States [Member]
Revenues by geographic area
Revenues									10,205	9,996	9,831
P&C Group [Member] | Reportable Geographical Components [Member] | International [Member]
Revenues by geographic area
Revenues									$ 3,297	$ 3,360	$ 3,411