Summary of Off-Balance Sheet Credit Transactions, Net of Participations (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Lending commitments
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Potential exposure of off-balance sheet credit risks	$ 28,737	[1]	$ 28,406	[1]
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Potential exposure of off-balance sheet credit risks	6,399	[2]	6,707	[2]
Commercial letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Potential exposure of off-balance sheet credit risks	294		437
Securities lending indemnifications
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Potential exposure of off-balance sheet credit risks	264,934		268,812
Support agreements
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Potential exposure of off-balance sheet credit risks	$ 70		$ 63

[1] Net of participations totaling $304 million at March 31, 2012 and $326 million at Dec. 31, 2011.

[2] Net of participations totaling $1.1 billion at March 31, 2012 and $1.2 billion at Dec. 31, 2011.