OTTI Losses on Available for Sale Securities (Detail) (USD $) In Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Net impairment losses recognized in earnings	$ 1		$ 1		$ 2		$ 2
Mortgage-backed Securities, Issued by Private Enterprises
Total OTTI losses	1		1		2		2
Portion of losses recognized in OCI (before taxes)		[1]		[1]		[1]		[1]
Net impairment losses recognized in earnings	$ 1		$ 1		$ 2		$ 2

[1] The initial OTTI amount represents the excess of the amortized cost over the fair value of AFS debt securities. For subsequent impairments of the same security, amount represents additional declines in the fair value subsequent to the previously recorded OTTI, if applicable, until such time the security is no longer in an unrealized loss position.