Investment Securities - Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from sale	$ 55,744	$ 88,054	$ 132,868
Sales Transactions:
Gross gains	305	0	291
Gross losses	(277)	(284)	(243)
Total gain (losses) from sales transactions	28	(284)	48
Maturities, calls and impairment:
Gross gains	589	131	502
Gross losses	0	0	0
Other-than-temporary impairment	0	0	0
Total gain (losses) maturities and impairment	589	131	502
Net gains (losses) and impairment	$ 617	$ (153)	$ 550