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Fair Value Option - Changes in Fair Value Included in Foreign Exchange and Other Trading Activities (Detail) (Long-term Debt, USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Long-term Debt
   
Fair Value, Option, Quantitative Disclosures [Line Items]    
Changes in fair value under the fair value option election $ 6 [1] $ 1 [1]
[1] The change in fair value of the long-term debt is approximately offset by an economic hedge included in trading.