Investment Securities Held to Maturity - Disclosure Regarding Length of Time on Investment Securities with Temporary Impairment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	$ 31,350	$ 38,302
12 months or longer, Fair value	18,768	47,079
Total, fair value	50,118	85,381
Less than 12 months, gross unrealized losses	(189)	(269)
12 months or longer, gross unrealized losses	(339)	(769)
Total, gross unrealized losses	(528)	(1,038)
Agency Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	1,244	3,735
12 months or longer, Fair value	278	0
Total, fair value	1,522	3,735
Less than 12 months, gross unrealized losses	(6)	(20)
12 months or longer, gross unrealized losses	(2)	0
Total, gross unrealized losses	(8)	(20)
State and Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	24,266	27,679
12 months or longer, Fair value	17,746	47,079
Total, fair value	42,012	74,758
Less than 12 months, gross unrealized losses	(165)	(217)
12 months or longer, gross unrealized losses	(330)	(769)
Total, gross unrealized losses	(495)	(986)
Corporate Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	5,840	6,888
12 months or longer, Fair value	744	0
Total, fair value	6,584	6,888
Less than 12 months, gross unrealized losses	(18)	(32)
12 months or longer, gross unrealized losses	(7)	0
Total, gross unrealized losses	$ (25)	$ (32)