OTTI Losses on Available for Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	$ 0		$ 1
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	0		0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	0		1	[1]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	$ 0	[2]	$ 1	[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] Total OTTI was $0 for the three months ended March 31, 2014 and 2013. Of total OTTI, losses of $0 and $1 million were recognized in earnings, and gains of $0 and $1 million were recognized as non-credit-related OTTI in OCI for the three months ended March 31, 2014 and 2013, respectively.