Guarantee Arrangements and Pledged Assets - 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	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Disclosure Guarantee Arrangements And Pledged Assets Trend In Repurchase Demands Received On Loans Sold To G S Es And Other Third Parties By Loan Origination Vintage [Abstract]
Pre- 2004	$ 7		$ 5		$ 14
2004	21		13		31
2005	28		24		24
2006	80		56		41
2007	209		146		161
2008	123		98		112
Post 2008	18		68		34
Total repurchase demands received	$ 486	[1]	$ 410	[1]	$ 417	[1]

[1] Includes repurchase demands on loans sourced from our legacy broker channel of $393 million, $300 million and $339 million at December 2012, 2011 and 2010, respectively.