Subsequent Event - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Oct. 08, 2015
Subsequent Event [Line Items]
Gain on sale of securities		$ 284	$ 7,121	$ 819
Scenario Forecast [Member]
Subsequent Event [Line Items]
Gain on sale of securities	$ 2,100
Subsequent Event [Member] | Bank of Commerce [Member]
Subsequent Event [Line Items]
Total assets acquired					$ 196,000
Loans					$ 148,000
Percentage of voting interests acquired					100.00%
Deposits					$ 170,000
Equity capital					$ 22,000