Loans and Allowance for Loan Losses - Summary of Impaired Financial Receivables (Summary of Excluding Purchased Non-Covered and Covered Loans) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings not included above	$ 20,900,000	$ 23,900,000
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	29,203,000	38,885,000	70,823,000	79,289,000	96,131,000
Troubled debt restructurings not included above	17,214,000	18,744,000	17,951,000
Total impaired loans	46,417,000	57,629,000	88,774,000
Impaired loans not requiring a related allowance
Impaired loans requiring a related allowance	46,417,000	57,629,000	88,774,000
Allowance related to impaired loans	3,871,000	5,115,000	18,478,000
Average investment in impaired loans	51,721,000	70,209,000	88,320,000
Interest income recognized on impaired loans	522,000	495,000	637,000
Foregone interest income on impaired loans	$ 418,000	$ 718,000	$ 613,000