Securities - Summary of Securities Available-for-Sale and Restricted Stock (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Gross Unrealized Gains, Equity securities	$ 4
Fair Value, Equity securities	94	$ 89
Amortized Cost, Available-for-sale	92,817	98,205
Gross Unrealized Gains, Available-for-sale	74	406
Gross Unrealized Losses, Available-for-sale	2,083	948
Fair Value, Available-for-sale	90,808	97,663
Amortized Cost, Held to maturity	21,882	25,758
Gross Unrealized Gains, Held to maturity	18	111
Gross Unrealized Losses, Held to maturity	727	378
Fair Value, Held to maturity	21,173	25,491
Amortized Cost	119,366	128,630
Gross Unrealized Gains	133	553
Gross Unrealized Losses	2,810	1,326
Fair Value	116,689	127,857
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Equity securities	53	53
Gross Unrealized Gains, Equity securities	41	36
Gross Unrealized Losses, Equity securities	0	0
Fair Value, Equity securities	94	89
U.S. Treasury Security [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	993	999
Gross Unrealized Losses, Available-for-sale	1	1
Fair Value, Available-for-sale	992	998
U.S. Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	8,350	8,350
Gross Unrealized Losses, Available-for-sale	259	121
Fair Value, Available-for-sale	8,091	8,229
Amortized Cost, Held to maturity	9,479	9,477
Gross Unrealized Gains, Held to maturity	4	16
Gross Unrealized Losses, Held to maturity	452	228
Fair Value, Held to maturity	9,031	9,265
Mortgage-Backed Securities of Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	45,948	50,136
Gross Unrealized Gains, Available-for-sale	24	146
Gross Unrealized Losses, Available-for-sale	1,233	581
Fair Value, Available-for-sale	44,739	49,701
Amortized Cost, Held to maturity	12,403	11,581
Gross Unrealized Gains, Held to maturity	14	95
Gross Unrealized Losses, Held to maturity	275	145
Fair Value, Held to maturity	12,142	11,531
Asset-Backed Securities of Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	1,104	1,168
Gross Unrealized Gains, Available-for-sale		1
Gross Unrealized Losses, Available-for-sale	3
Fair Value, Available-for-sale	1,101	1,169
State and Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	26,419	27,020
Gross Unrealized Gains, Available-for-sale	47	224
Gross Unrealized Losses, Available-for-sale	349	103
Fair Value, Available-for-sale	26,117	27,141
Amortized Cost, Held to maturity		4,700
Gross Unrealized Losses, Held to maturity		5
Fair Value, Held to maturity		4,695
Corporate Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost, Available-for-sale	10,003	10,532
Gross Unrealized Gains, Available-for-sale	3	35
Gross Unrealized Losses, Available-for-sale	238	142
Fair Value, Available-for-sale	9,768	10,425
Restricted Stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost	4,614	4,614
Fair Value	$ 4,614	$ 4,614

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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