Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary Information Related to Commitments to Extend Credit (Excluding Letters of Credit) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Disclosure Off Balance Sheet Arrangements Guarantees And Other Commitments Additional Information [Abstract]
Fixed interest rate commitments	$ 1,341,917	[1]	$ 1,392,781	[1]
Variable interest rate commitments	10,016,728	[1]	9,101,973	[1]
Total loan commitments available for funding	11,358,645	[1]	10,494,754	[1]
Commercial and standby letters of credit	1,012,651	[2]	975,968	[2]
Total unfunded credit commitments	12,371,296		11,470,722
Commitments unavailable for funding	1,161,940	[3]	1,006,168	[3]
Maximum lending limits for accounts receivable factoring arrangements	930,643	[4]	894,276	[4]
Reserve for unfunded credit commitments	$ 31,110	[5]	$ 29,983	[5]

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

[2] See below for additional information on our commercial and standby letters of credit.

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

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

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