Mortgage Loan Repurchase Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Reserve for mortgage loan repurchase losses
Balance at beginning of period	$ 320	$ 265
Repurchase provision	175	80
Charge-offs	(112)	(75)
Balance at end of period	$ 383	$ 270