Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Long-term Purchase Commitment
Commitments	$ 4,194
Commitments to Extend Credit
Long-term Purchase Commitment
Commitments	63,021	62,050
Financial Standby Letter of Credit
Long-term Purchase Commitment
Commitments	1,844	1,448
Forward Contracts
Long-term Purchase Commitment
Commitments	4,194	4,129
Noncancelable Lease Obligations
Long-term Purchase Commitment
Commitments	729	746
Private Equity Funds
Long-term Purchase Commitment
Commitments	95	90
Purchase Commitment
Long-term Purchase Commitment
Commitments	80	84
Capital Additions
Long-term Purchase Commitment
Commitments	29	33
Capital Lease Obligations
Long-term Purchase Commitment
Commitments	$ 17	$ 19