Rollforward of Credit Losses Recognized in Earnings Related to Securities (Detail) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Schedule of Available-for-sale Securities [Line Items]
Beginning balance	$ 20	$ 22
Additions/reductions	2	(1)	[1]
Increases in expected cash flows recognized over the remaining life of the securities	(1)
Ending balance	$ 21	$ 21

[1] During the nine months ended September 30, 2010, the Company recognized $2 million of OTTI through earnings on debt securities in which no portion of the OTTI loss was included in OCI at any time during the period. OTTI related to these securities are excluded from this amount.