Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred loan fee income	$ 89,000,000				$ 89,000,000				$ 77,000,000
Loans modified in TDRs	29,273,000				29,273,000				34,328,000
Unfunded commitments available for funding	400,000				400,000
Loans modified in TDRs during the period	7,337,000	[1]	1,969,000	[1]	9,653,000	[1]	16,431,000	[1]
Forgiveness Of Principal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified in TDRs during the period							9,600,000
Payment Deferrals Granted
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified in TDRs during the period	$ 7,300,000		$ 2,000,000		$ 9,600,000		$ 6,800,000

[1] the three and nine months ended September 30, 2013, respectively. There were partial charge-offs of $1.1 million and $11.0 million, respectively, on loans classified as TDRs during the three and nine months ended September 30, 2012.