Summary Information Related to Commitments to Extend Credit (Excluding Letters of Credit) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Supply Commitment [Line Items]
Fixed interest rate commitments	$ 658,377	[1]	$ 386,055	[1]
Variable interest rate commitments	6,548,002	[1]	5,884,450	[1]
Total commitments available for funding	7,206,379	[1]	6,270,505	[1]
Commitments unavailable for funding	841,439	[2]	963,847	[2]
Maximum lending limits for accounts receivable factoring arrangements	747,392	[3]	697,702	[3]
Reserve for unfunded credit commitments	$ 21,811	[4]	$ 17,414	[4]

[1] Represents commitments which are available for funding, due to clients meeting all collateral, compliance and financial covenants required under loan commitment agreements.

[2] Represents commitments which are currently unavailable for funding, due to clients failing to meet all collateral, compliance and financial covenants under loan commitment agreements.

[3] We extend credit under accounts receivable factoring arrangements when our clients' sales invoices are deemed creditworthy under existing underwriting practices.

[4] Our reserve for unfunded credit commitments includes an allowance for both our unfunded loan commitments and our letters of credit.