Securities-Debt Securities Credit Losses Roll Forward Recorded in Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other than Temporary Impairment [Roll Forward]
Beginning balance	$ 164	$ 333	$ 288	$ 253
Add: Initial OTTI credit losses	0	2	16	52
Subsequent OTTI credit losses	3	4	10	42
Less: Realized losses for securities sold	2	77	149	85
Ending balance	$ 165	$ 262	$ 165	$ 262