Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) (USD $) In Billions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Total	$ 5,225.3	$ 4,729.8
Interest rate contracts [Member]
Derivative [Line Items]
Total	3,651.6	3,244.0
Interest rate contracts [Member] | Futures and forwards [Member]
Derivative [Line Items]
Total	209.9	313.9
Interest rate contracts [Member] | Swaps [Member]
Derivative [Line Items]
Total	3,400.3	2,842.6
Interest rate contracts [Member] | Options written [Member]
Derivative [Line Items]
Total	19.1	43.3
Interest rate contracts [Member] | Options purchased [Member]
Derivative [Line Items]
Total	22.3	44.2
Foreign exchange contracts [Member]
Derivative [Line Items]
Total	1,060.6	910.4
Foreign exchange contracts [Member] | Options written [Member]
Derivative [Line Items]
Total	79.7	54.9
Foreign exchange contracts [Member] | Options purchased [Member]
Derivative [Line Items]
Total	80.2	55.5
Foreign exchange contracts [Member] | Swaps, futures and forwards [Member]
Derivative [Line Items]
Total	830.8	743.7
Foreign exchange contracts [Member] | Spot [Member]
Derivative [Line Items]
Total	69.9	56.3
Commodity and Equity Contract [Member]
Derivative [Line Items]
Total	93.9	90.5
Commodity and Equity Contract [Member] | Options written [Member]
Derivative [Line Items]
Total	21.8	21.0
Commodity and Equity Contract [Member] | Options purchased [Member]
Derivative [Line Items]
Total	22.2	21.4
Commodity and Equity Contract [Member] | Swaps, futures and forwards [Member]
Derivative [Line Items]
Total	49.9	48.1
Credit contracts [Member]
Derivative [Line Items]
Total	$ 419.2	$ 484.9