Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Derivative [Line Items]
This amount represents additional cash collateral received from derivative counterparties not offset against derivative assets and liabilities	$ 8,400,000		$ 72,300,000
This amount represents additional cash collateral deposited with derivative counterparties not offset against derivative assets and liabilities	214,200,000		47,800,000
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	181,200,000		202,000,000
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	338,600,000		80,500,000
Termination payments that could have been required for derivative instruments with credit-risk-related contingent features	0		121,500,000
Sterling denominated debt designated as hedges of foreign exchange risk	240,400,000		241,200,000
Maximum length of time being hedged for exposure to variability in future cash flows of forecasted foreign currency denominated transactions	Twenty-three months is the maximum length of time over which the exposure to variability in future cash flows of forecasted foreign currency denominated transactions is being hedged.
Net foreign exchange contract losses reclassified from AOCI	0	0
Estimated net gain (loss) to be reclassified into earnings within the next twelve months relating to cash flow hedges	2,800,000
Derivative Financial Instruments, Assets
Derivative [Line Items]
Derivative assets recorded on the consolidated balance sheet, reduced as a result of master netting agreements	1,800,000,000		2,000,000,000
Reduction in derivative assets (liabilities) due to cash collateral received from (deposited with) derivative counterparties	350,300,000		220,100,000
Derivative Financial Instruments, Liabilities
Derivative [Line Items]
Derivative liabilities recorded on the consolidated balance sheet, reduced as a result of master netting agreements	1,800,000,000		2,000,000,000
Reduction in derivative assets (liabilities) due to cash collateral received from (deposited with) derivative counterparties	293,100,000		257,400,000
Client Related and Trading
Derivative [Line Items]
Percentage of derivatives outstanding related to client-related and trading activities	0.97%		0.97%
Changes recorded in the fair value of the hedged items in a fair value hedge	300,000	300,000
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	$ 600,000	$ 200,000