Guarantee Arrangements and Pledged Assets and Collateral - Summary of Pledged Assets Included in Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Interest bearing deposits with banks	$ 535		$ 673
Trading assets	3,434	[1]	2,346	[1]
Securities available-for-sale	19,976	[2]	17,236	[2]
Securities held to maturity	587		456
Loans	3,953	[3]	2,142	[3]
Other assets	2,692	[4]	2,265	[4]
Total	$ 31,177		$ 25,118

[1] Trading assets are primarily pledged against liabilities associated with repurchase agreements.

[2] Securities available-for-sale are primarily pledged against derivatives, public fund deposits and various short-term and long term borrowings, as well as providing capacity for potential secured borrowings from the Federal Home Loan Bank and the Federal Reserve Bank.

[3] Loans are primarily residential mortgage loans pledged against long-term borrowings from the Federal Home Loan Bank.

[4] Other assets represent cash on deposit with non-banks related to derivative collateral support agreements.