Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended	12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Net Investment Hedges	Dec. 31, 2013 Net Investment Hedges	Jun. 30, 2014 Client Related and Trading	Dec. 31, 2013 Client Related and Trading
Derivative [Line Items]
Derivative assets recorded on the consolidated balance sheet, reduced as a result of master netting agreements	$ 900,000,000		$ 900,000,000		$ 1,200,000,000
Derivative liabilities recorded on the consolidated balance sheet, reduced as a result of master netting agreements	900,000,000		900,000,000		1,200,000,000
Reduction in derivative assets due to cash collateral received from derivative counterparties	552,000,000		552,000,000		210,700,000
Reduction in derivative liabilities due to cash collateral deposited with derivative counterparties	581,100,000		581,100,000		767,700,000
This amount represents additional cash collateral received from derivative counterparties not offset against derivative assets	102,900,000		102,900,000		36,400,000
This amount represents additional cash collateral deposited with derivative counterparties not offset against derivative liabilities	2,100,000		2,100,000		39,300,000
Securities posted as collateral	27,500,000		27,500,000		27,600,000
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	577,600,000		577,600,000		257,300,000
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	554,300,000		554,300,000		197,000,000
Termination payments that could have been required for derivative instruments with credit-risk-related contingent features	23,300,000		23,300,000		60,300,000
Percentage of derivatives outstanding related to client-related and trading activities								97.00%	97.00%
Sterling denominated debt designated as hedges of foreign exchange risk						260,700,000	259,100,000
Changes recorded in the fair value of the hedged items in a fair value hedge	0	300,000	0	600,000
The net gain/loss recognized in earnings during the period representing the amount of hedge ineffectiveness for fair value hedges of available for sale investment securities, senior notes, or subordinated debt	0	300,000	0	500,000
Maximum length of time being hedged for exposure to variability in future cash flows of forecasted foreign currency denominated transactions			23 months
The net gain/loss recognized in earnings during the period representing the amount of hedge ineffectiveness cash flow hedges	0	0	0	0
Net foreign exchange contract gains (losses) reclassified from AOCI	0	0	0	0
Estimated net gain (loss) to be reclassified into earnings within the next twelve months relating to cash flow hedges			5,300,000
Ineffectiveness from net investment hedges	$ 0	$ 0	$ 0	$ 0