Commitments and Contingencies - Summary of Obligations (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Credit related obligations	$ 4,373,679	$ 4,189,421
Letters of credit [Member]
Loss Contingencies [Line Items]
Credit related obligations	$ 401,861	$ 441,048

- Definition

Represents the caption on the face of the balance sheet to indicate that the entity has entered into (1) purchase or supply arrangements that will require expending a portion of its resources to meet the terms thereof, and (2) is exposed to potential losses or, less frequently, gains, arising from (a) possible claims against a company's resources due to future performance under contract terms, and (b) possible losses or likely gains from uncertainties that will ultimately be resolved when one or more future events that are deemed likely to occur do occur or fail to occur.

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