Offsetting of Derivative Liabilities and of Securities Sold Under Agreements to Repurchase Within Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Amounts Presented	$ 546.6	$ 885.1
Derivatives
Derivative [Line Items]
Gross Recognized Liabilities	2,661.5	4,227.3
Gross Amounts Offset	1,717.6	3,173.3
Net Amounts Presented	943.9	1,054.0
Derivative Liability	943.9	1,054.0
Derivatives | Subject to Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	2,261.8	3,562.8
Gross Amounts Offset	1,717.6	3,173.3
Net Amounts Presented	544.2	389.5
Derivative Liability	544.2	389.5
Derivatives | Not Subject to Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	399.7	664.5
Net Amounts Presented	399.7	664.5
Derivative Liability	399.7	664.5
Derivatives | Foreign Exchange Contracts | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	2,119.7	3,431.0
Gross Amounts Offset	1,194.3	1,889.8
Net Amounts Presented	925.4	1,541.2
Derivative Liability	925.4	1,541.2
Derivatives | Interest Rate Swaps | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	93.1	118.7
Gross Amounts Offset	21.5	32.1
Net Amounts Presented	71.6	86.6
Derivative Liability	71.6	86.6
Derivatives | Interest Rate Swaps | Exchange Cleared
Derivative [Line Items]
Gross Recognized Liabilities	38.1	13.1
Gross Amounts Offset	38.1	13.1
Derivatives | Other Financial Derivative [Member] | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	10.9
Net Amounts Presented	10.9
Derivative Liability	10.9
Derivatives | Cross Product Netting Adjustment
Derivative [Line Items]
Gross Amounts Offset	23.5	6.3
Derivatives | Cross Product Collateral Adjustment
Derivative [Line Items]
Gross Amounts Offset	440.2	1,232.0
Securities Sold under Agreements to Repurchase
Derivative [Line Items]
Gross Recognized Liabilities	546.6	885.1
Gross Amounts Not Offset	(546.6)	(885.1)
Net Amounts Presented	$ 546.6	$ 885.1