Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Commitments to Extend Credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 63,379	$ 62,050
Financial Standby Letter of Credit
Long-term Purchase Commitment [Line Items]
Commitments	3,931	4,129
Forward Contracts
Long-term Purchase Commitment [Line Items]
Commitments	977	1,448
Noncancelable Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	708	746
Private Equity Funds
Long-term Purchase Commitment [Line Items]
Commitments	85	90
Purchase Commitment
Long-term Purchase Commitment [Line Items]
Commitments	79	84
Capital Additions
Long-term Purchase Commitment [Line Items]
Commitments	34	33
Capital Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 14	$ 19