Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Total	$ 5,318.5	$ 4,729.8
Interest rate contracts [Member]
Derivative [Line Items]
Total	3,848.8	3,244.0
Interest rate contracts [Member] | Futures and forwards [Member]
Derivative [Line Items]
Total	182.0	313.9
Interest rate contracts [Member] | Swaps [Member]
Derivative [Line Items]
Total	3,472.0	2,842.6
Interest rate contracts [Member] | Options written [Member]
Derivative [Line Items]
Total	97.3	43.3
Interest rate contracts [Member] | Options purchased [Member]
Derivative [Line Items]
Total	97.5	44.2
Foreign exchange contracts [Member]
Derivative [Line Items]
Total	975.9	910.4
Foreign exchange contracts [Member] | Options written [Member]
Derivative [Line Items]
Total	77.0	54.9
Foreign exchange contracts [Member] | Options purchased [Member]
Derivative [Line Items]
Total	79.0	55.5
Foreign exchange contracts [Member] | Swaps, futures and forwards [Member]
Derivative [Line Items]
Total	756.6	743.7
Foreign exchange contracts [Member] | Spot [Member]
Derivative [Line Items]
Total	63.3	56.3
Commodity and Equity Contract [Member]
Derivative [Line Items]
Total	90.8	90.5
Commodity and Equity Contract [Member] | Options written [Member]
Derivative [Line Items]
Total	21.6	21.0
Commodity and Equity Contract [Member] | Options purchased [Member]
Derivative [Line Items]
Total	22.0	21.4
Commodity and Equity Contract [Member] | Swaps, futures and forwards [Member]
Derivative [Line Items]
Total	47.2	48.1
Credit contracts [Member]
Derivative [Line Items]
Total	$ 403.0	$ 484.9