Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Amounts Presented	$ 484,500,000	$ 885,100,000
Other liabilities	2,500,000,000	2,800,000,000
Cash collateral placed that was not offset	0	0
Securities Sold under Agreements to Repurchase
Derivative [Line Items]
Gross Recognized Liabilities	484,500,000	885,100,000
Net Amounts Presented	484,500,000	885,100,000
Gross Amounts Not Offset	(484,500,000)	(885,100,000)
Derivatives
Derivative [Line Items]
Gross Recognized Liabilities	2,951,000,000	4,227,300,000
Gross Amounts Offset	2,261,300,000	3,173,300,000
Net Amounts Presented	689,700,000	1,054,000,000
Net Amount (2)	689,700,000	1,054,000,000
Derivatives | Total Derivatives Subject to a Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	2,550,300,000	3,562,800,000
Gross Amounts Offset	2,261,300,000	3,173,300,000
Net Amounts Presented	289,000,000	389,500,000
Net Amount (2)	289,000,000	389,500,000
Derivatives | Total Derivatives Not Subject to a Master Netting Arrangement
Derivative [Line Items]
Gross Recognized Liabilities	400,700,000	664,500,000
Net Amounts Presented	400,700,000	664,500,000
Net Amount (2)	400,700,000	664,500,000
Derivatives | Foreign Exchange Contracts | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	2,373,900,000	3,431,000,000
Gross Amounts Offset	1,002,100,000	1,889,800,000
Net Amounts Presented	1,371,800,000	1,541,200,000
Net Amount (2)	1,371,800,000	1,541,200,000
Derivatives | Interest Rate Swap Contracts | Over the Counter Derivative
Derivative [Line Items]
Gross Recognized Liabilities	113,900,000	118,700,000
Gross Amounts Offset	29,700,000	32,100,000
Net Amounts Presented	84,200,000	86,600,000
Net Amount (2)	84,200,000	86,600,000
Derivatives | Interest Rate Swap Contracts | Exchange Cleared
Derivative [Line Items]
Gross Recognized Liabilities	51,600,000	13,100,000
Gross Amounts Offset	51,600,000	13,100,000
Derivatives | Other Financial Derivatives (1)
Derivative [Line Items]
Gross Recognized Liabilities	10,900,000
Net Amounts Presented	10,900,000
Net Amount (2)	10,900,000
Derivatives | Cross Product Netting Adjustment
Derivative [Line Items]
Gross Amounts Offset	14,600,000	6,300,000
Derivatives | Cross Product Collateral Adjustment
Derivative [Line Items]
Gross Amounts Offset	$ 1,163,300,000	$ 1,232,000,000