Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Long-term Purchase Commitment
Commitments	$ 3,978
Commitments to Extend Credit
Long-term Purchase Commitment
Commitments	62,121	62,050
Financial Standby Letter of Credit
Long-term Purchase Commitment
Commitments	3,978	4,129
Forward Contracts
Long-term Purchase Commitment
Commitments	1,074	1,448
Noncancelable Lease Obligations
Long-term Purchase Commitment
Commitments	728	746
Private Equity Funds
Long-term Purchase Commitment
Commitments	91	90
Purchase Commitment
Long-term Purchase Commitment
Commitments	86	84
Capital Additions
Long-term Purchase Commitment
Commitments	30	33
Capital Lease Obligations
Long-term Purchase Commitment
Commitments	$ 16	$ 19