Derivative Financial Instruments (Location and Amount of Gains and Losses Recorded in Income) (Details) - Client Related and Trading - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gain/(loss) recognized in income	$ 64.6	$ 76.5
Foreign Exchange Contracts | Foreign Exchange Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gain/(loss) recognized in income	60.5	71.6
Interest Rate Contracts | Security Commissions and Trading Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gain/(loss) recognized in income	$ 4.1	$ 4.9