Securities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Securities pledged for public funds	$ 138,500,000			$ 107,100,000
Available for sale securities transferred to held to maturity, total amortized cost		$ 105,300,000
Available for sale securities transferred to held to maturity fair value		103,800,000
Net unrealized loss, net of taxes, on securities at date of transfer		$ (999,000)
Proceeds from the sale of securities available for sale	18,134,000		$ 5,153,000
Gross gains realized on sales of securities available for sale	153,000		11,000
Income tax expense related to net realized gains	$ 54,000		$ 4,000