Derivative Financial Instruments (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Derivative [Line Items]
Derivative liabilities recorded on the consolidated balance sheet, reduced as a result of master netting agreements	$ 1,300,000,000		$ 1,300,000,000		$ 1,300,000,000
Derivative asset, fair value, amount offset against collateral	364,300,000		364,300,000		264,300,000
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	128,500,000		128,500,000		544,200,000
Gains or losses reclassified into earnings	0	$ 0	$ 0	$ 0
Maximum length of time over which exposure was being hedged			23 months
Securities posted as collateral	51,100,000		$ 51,100,000		15,400,000
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	688,100,000		688,100,000		553,200,000
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	665,000,000		665,000,000		163,000,000
Termination payments that could have been required for derivative instruments with credit-risk-related contingent features	23,100,000		23,100,000		390,200,000
Ineffectiveness or changes in the fair value of hedged items recognized in earnings for fair value hedges	0	0	0	0
Ineffectiveness recognized in earnings for cash flow hedges	0	0	0	0
Ineffectiveness from net investment hedges	0	$ 0	0	$ 0
Net Investment Hedges
Derivative [Line Items]
Derivative assets recorded on the consolidated balance sheet, reduced as a result of master netting agreements	1,300,000,000		1,300,000,000		1,300,000,000
Derivative asset, fair value, amount offset against collateral	339,000,000		339,000,000		322,800,000
Gross Amount of Recognized Liabilities for Repurchase Agreements in Note 21	768,500,000		768,500,000		440,200,000
This amount represents additional cash collateral received from derivative counterparties not offset against derivative assets	34,000,000		34,000,000		31,100,000
This amount represents additional cash collateral deposited with derivative counterparties not offset against derivative liabilities	$ 98,400,000		$ 98,400,000		$ 27,300,000
Client Related and Trading
Derivative [Line Items]
Percentage of derivatives outstanding related to client-related and trading activities	96.00%		96.00%		97.00%
Foreign Currency Denominate
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges			$ (700,000)
Forecasted Foreign Currency Denominated Investment Securities
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges			(6,700,000)
Securities Available for Sale
Derivative [Line Items]
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges			$ 1,600,000