Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Net Amounts Presented	$ 507,100,000	$ 546,600,000
Other liabilities	2,008,700,000	2,131,700,000
Cash collateral placed that was not offset	0	0
Securities Sold under Agreements to Repurchase
Derivative [Line Items]
Gross Recognized Liabilities	507,100,000	546,600,000
Net Amounts Presented	507,100,000	546,600,000
Gross Amounts Not Offset	(507,100,000)	(546,600,000)
Derivatives
Derivative [Line Items]
Gross Recognized Liabilities	4,253,900,000	2,661,500,000
Gross Amounts Offset	2,916,000,000	1,717,600,000
Net Amounts Presented	1,337,900,000	943,900,000
Net Amount	1,337,900,000	943,900,000
Derivatives | Total Derivatives Subject to a Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	3,435,800,000	2,261,800,000
Gross Amounts Offset	2,916,000,000	1,717,600,000
Net Amounts Presented	519,800,000	544,200,000
Net Amount	519,800,000	544,200,000
Derivatives | Total Derivatives Not Subject to a Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	818,100,000	399,700,000
Net Amounts Presented	818,100,000	399,700,000
Net Amount	818,100,000	399,700,000
Foreign Exchange Contracts | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	3,210,300,000	2,119,700,000
Gross Amounts Offset	1,523,100,000	1,194,300,000
Net Amounts Presented	1,687,200,000	925,400,000
Net Amount	1,687,200,000	925,400,000
Interest Rate Swap Contracts | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	118,300,000	93,100,000
Gross Amounts Offset	22,300,000	21,500,000
Net Amounts Presented	96,000,000	71,600,000
Net Amount	96,000,000	71,600,000
Interest Rate Swap Contracts | Exchange Cleared
Derivative [Line Items]
Gross Recognized Liabilities	96,800,000	38,100,000
Gross Amounts Offset	96,800,000	38,100,000
Other Financial Derivatives
Derivative [Line Items]
Gross Recognized Liabilities	10,400,000	10,900,000
Net Amounts Presented	10,400,000	10,900,000
Net Amount	10,400,000	10,900,000
Cross Product Netting Adjustment
Derivative [Line Items]
Gross Amounts Offset	42,400,000	23,500,000
Cross Product Collateral Adjustment
Derivative [Line Items]
Gross Amounts Offset	$ 1,231,400,000	$ 440,200,000