Securities - Aggregate Amortized Costs and Fair Values of Available-for-Sale Securities Portfolio (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 54,718	$ 51,929
Gross Unrealized Gains	341	116
Gross Unrealized (Losses)	(611)	(872)
Fair Value	54,448	51,173	[1]
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,696	7,695
Gross Unrealized Gains	20	14
Gross Unrealized (Losses)	(1)	(5)
Fair Value	6,715	7,704
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,319	25,668
Gross Unrealized Gains	123	53
Gross Unrealized (Losses)	(386)	(408)
Fair Value	27,056	25,313
State and Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,703	18,566
Gross Unrealized Gains	198	49
Gross Unrealized (Losses)	(224)	(459)
Fair Value	$ 20,677	$ 18,156

[1] Derived from the audited December 31, 2016 Consolidated Financial Statements