Investment Securities - Information Related to Sales of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Securities available-for-sale:
Proceeds from sales	$ 77,308	$ 32,967	$ 76,361
Gross realized gains on sales	1,295	635	3,396
Gross realized losses on sales	30	0	7
Tax expense related to net realized gains on sales	$ 443	$ 222	$ 1,186