Mortgage Loan Repurchase Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Reserve for mortgage loan repurchase losses
Balance at beginning of period	$ 383	$ 270	$ 320	$ 265
Repurchase provision	155	90	330	170
Charge-offs	(104)	(61)	(216)	(136)
Balance at end of period	$ 434	$ 299	$ 434	$ 299