Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Commitments to Extend Credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 63,827	$ 62,050
Financial Standby Letter of Credit
Long-term Purchase Commitment [Line Items]
Commitments	3,974	4,129
Forward Contracts
Long-term Purchase Commitment [Line Items]
Commitments	999	1,448
Noncancelable Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	697	746
Private Equity Funds [Member]
Long-term Purchase Commitment [Line Items]
Commitments	78	90
Purchase Commitment
Long-term Purchase Commitment [Line Items]
Commitments	77	84
Capital Additions
Long-term Purchase Commitment [Line Items]
Commitments	28	33
Capital Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 37	$ 19