Guarantee Arrangements and Pledged Assets and Collateral - Trend in Repurchase Demands Received on Loans Sold to GSEs and Other Third Parties by Loan Origination Vintage (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
Commitments and Contingencies Disclosure [Abstract]
Pre- 2004	$ 1		$ 2		$ 4		$ 5
2004	4		5		15		16
2005	13		6		20		19
2006	12		20		38		65
2007	25		51		86		170
2008	13		28		48		106
Post 2008	2		4		12		15
Total repurchase demands received	$ 70	[1]	$ 116	[1]	$ 223	[1]	$ 396	[1]

[1] Includes repurchase demands on loans sourced from our legacy broker channel of $55 million and $98 million for the three months ended September 30, 2013 and 2012, respectively, and $175 million and $330 million for the nine months ended September 30, 2013 and 2012, respectively.