Guarantee Arrangements and Pledged Assets and Collateral - Summary of Change in Estimated Repurchase Liability for Loans Sold to GSEs and Other Third Parties (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Estimated Repurchase Liability For Loans Sold [Roll Forward]
Balance at beginning of period	$ 36	$ 211	$ 99	$ 219
Increase (decrease) in liability recorded through earnings	0	23	(34)	36
Realized losses	(2)	(17)	(31)	(38)
Balance at end of period	$ 34	$ 217	$ 34	$ 217