Gains and Losses Recorded in Consolidated Statement of Income Related to Client Related and Trading Derivative Financial Instruments (Detail) (Client Related and Trading, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	$ 47.0	$ 67.2	$ 154.0	$ 205.0
Foreign Exchange Contracts | Foreign Exchange Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	46.4	62.8	149.4	193.6
Interest Rate Contracts | Security Commissions and Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Gain/(Loss) Recognized in Income	$ 0.6	$ 4.4	$ 4.6	$ 11.4