Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred loan fee income	$ 77,000,000		$ 60,000,000
Loans modified in TDRs	34,328,000		34,275,000
Financing Receivable, Modifications, Number of Contracts	18		17
Unfunded commitments available for funding	500,000
Loans modified in TDRs during the period	28,723,000	[1]	13,599,000	[1]
Forgiveness Of Principal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified in TDRs during the period	9,300,000
Payment Deferrals Granted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified in TDRs during the period	$ 19,400,000

[1] (1)During 2012 and 2011, we had partial charge-offs of $14.3 million and $2.8 million, respectively, on loans classified as TDRs.