Pledged Assets - Additional Information (Detail) (USD $)	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans served as collateral to secure debt obligations	$ 400,000,000	$ 500,000
Short-term and long-term credit facilities authorized with the Federal Home Loan Bank of New York	1,700,000,000	1,600,000,000	1,700,000,000
Investment securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments served as collateral to secure debt obligations	1,700,000,000	1,300,000,000	2,000,000,000
Loans Held for Investment
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans served as collateral to secure debt obligations	3,800,000,000	4,200,000,000	4,400,000,000
Loans-held-in portfolio served as collateral to secure credit facilities authorized with the FHLB	4,900,000,000	3,800,000,000
Loans Held for Investment and Available for sale Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Loans-held-in portfolio and investment securities available-for-sale served as collateral to secure credit facilities authorized with the FHLB			3,000,000,000
Covered under Loss Sharing Agreements with FDIC
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments served as collateral to secure debt obligations	4,400,000,000	4,800,000,000	4,900,000,000
Federal Reserve Bank Advances
Financial Instruments Owned and Pledged as Collateral [Line Items]
Remaining unused borrowing capacity at the Fed discount window	$ 2,500,000,000	$ 2,700,000,000	$ 2,700,000,000