Variable Interest Entities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum Exposure to Loss	$ 3,573	$ 2,470
Trading assets arising due to "failed sale" accounting treatment	78	73
Long-term liabilities arising due to "failed sale" accounting treatment	104	89
Asset-backed commercial paper conduits [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum Exposure to Loss	1,550	677
Credit card operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining balances related to consolidated VIEs as part of other assets	0
Balance related to consolidated VIEs of other liabilities		$ 541