Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Long-term Purchase Commitment [Line Items]
Commitments	$ 4,281
Commitments to Extend Credit [Member]
Long-term Purchase Commitment [Line Items]
Commitments	53,403	47,719
Financial Standby Letter of Credit
Long-term Purchase Commitment [Line Items]
Commitments	4,281	4,744
Forward Contracts
Long-term Purchase Commitment [Line Items]
Commitments	5,322	5,705
Noncancelable Lease Obligations [Member]
Long-term Purchase Commitment [Line Items]
Commitments	769	851
Private Equity Funds
Long-term Purchase Commitment [Line Items]
Commitments	121	166
Purchase Commitment
Long-term Purchase Commitment [Line Items]
Commitments	87	115
Capital Additions
Long-term Purchase Commitment [Line Items]
Commitments	29	41
Capital Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 24	$ 26

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents commitments outstanding as of the balance sheet date which obligate or represent potential claims against the assets of the Company relating to, for example, the extension of credit. Further, commitments generally represent off balance sheet arrangements that obligate the entity to deliver assets or services or enter into another obligation in the future.

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