Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Interest rate	$ 3,176.2	$ 2,782.6
Commodities, equities and precious metals	84.0	75.5
Foreign Exchange	1,002.6	865.2
Credit derivatives	526.0	657.3
Total	4,788.8	4,380.6
Futures And forwards [Member]
Derivative [Line Items]
Interest rate	389.3	320.3
Swap [Member]
Derivative [Line Items]
Interest rate	2,657.0	2,325.1
Options written [Member]
Derivative [Line Items]
Interest rate	64.9	69.9
Commodities, equities and precious metals	9.5	8.2
Foreign Exchange	51.9	39.7
Options purchased [Member]
Derivative [Line Items]
Interest rate	65.0	67.3
Commodities, equities and precious metals	20.4	17.1
Foreign Exchange	53.0	40.4
Swaps futures and forwards [Member]
Derivative [Line Items]
Commodities, equities and precious metals	54.1	50.2
Foreign Exchange	820.4	725.0
Spot [Member]
Derivative [Line Items]
Foreign Exchange	$ 77.3	$ 60.1