Credit Losses Recognized in Net Income on Debt Securities (Detail) (Debt Securities, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Cumulative credit losses, beginning balance	$ 387	$ 646	$ 784
Other-than-temporary impairments not previously recognized	4	16	39
Increases related to other-than-temporary impairments previously recognized	11	55	82
Securities sold, paid down or disposed	(301)	(330)	(259)
Cumulative credit losses, ending balance	$ 101	$ 387	$ 646