Summary of Significant Commitments (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Commitments to Extend Credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 46,019	$ 43,677	$ 43,003
Financial Standby Letter of Credit
Long-term Purchase Commitment [Line Items]
Commitments	4,949	5,516	5,847
Forward Contracts
Long-term Purchase Commitment [Line Items]
Commitments	4,602	6,389	7,637
Noncancelable Lease Obligations [Member]
Long-term Purchase Commitment [Line Items]
Commitments	856	869	874
Private Equity Funds
Long-term Purchase Commitment [Line Items]
Commitments	178	193	176
Purchase Commitment
Long-term Purchase Commitment [Line Items]
Commitments	117	64	42
Capital Additions
Long-term Purchase Commitment [Line Items]
Commitments	42	48	44
Capital Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 25	$ 32	$ 38