Mortgage Loan Repurchase Losses (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
Reserve for mortgage loan repurchase losses
Balance at beginning of period	$ 513	$ 383	$ 632	$ 320
Repurchase provision	15	155	29	330
Charge-offs	(165)	(104)	(298)	(216)
Balance at end of period	$ 363	$ 434	$ 363	$ 434