Investment Securities (Unrealized Losses and Related Fair Values in Company's Held to Maturity and Available for Sale Investment Securities Portfolios) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 45,515	$ 20,255
Less than 12 months, unrealized losses	(1,025)	(284)
12 months or more, fair value	4,037	6,722
12 months or more, unrealized losses	(182)	(162)
Total, fair value	49,552	26,977
Total, unrealized losses	(1,207)	(446)
Government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value		897
Less than 12 months, unrealized losses		(16)
12 months or more, fair value	1,924	3,910
12 months or more, unrealized losses	(73)	(85)
Total, fair value	1,924	4,807
Total, unrealized losses	(73)	(101)
Collateralized Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	31,759	9,357
Less than 12 months, unrealized losses	(789)	(68)
12 months or more, fair value	688	782
12 months or more, unrealized losses	(34)	(25)
Total, fair value	32,447	10,139
Total, unrealized losses	(823)	(93)
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	1,548	2,974
Less than 12 months, unrealized losses	(12)	(130)
12 months or more, fair value	1,425
12 months or more, unrealized losses	(75)
Total, fair value	2,973	2,974
Total, unrealized losses	(87)	(130)
State and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	12,208	5,512
Less than 12 months, unrealized losses	(224)	(52)
12 months or more, fair value		2,030
12 months or more, unrealized losses		(52)
Total, fair value	12,208	7,542
Total, unrealized losses	$ (224)	(104)
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value		1,515
Less than 12 months, unrealized losses		(18)
Total, fair value		1,515
Total, unrealized losses		$ (18)