OTTI Losses on Available for Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	$ 0		$ 2		$ 1		$ 4
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	0	[1]	0	[1]	0	[1]	0	[1]
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	0		2		1		4
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	$ 0	[2]	$ 2	[2]	$ 1		$ 4	[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 includes 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.

[2] Includes credit-related OTTI losses of $0 and $2 million that were unrealized losses reclassified from OCI, before taxes, for the three months ended June 30, 2013 and 2012, respectively, and $1 million and $4 million that were unrealized losses reclassified from OCI, before taxes, for the six months ended June 30, 2013 and 2012, respectively.