Investment Securities - Information Related to Sales of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Securities available-for-sale:
Proceeds from sales	$ 77,290	$ 77,308	$ 32,967
Gross realized gains on sales	600	1,295	635
Gross realized losses on sales	82	30	0
Tax expense related to net realized gains on sales	$ 181	$ 443	$ 222