Securities - Amortized Cost and Fair Value of Securities with Gross Unrealized Gains and Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 176,723	$ 172,263
Gross Unrealized Gains	530	295
Gross Unrealized Losses	(2,571)	(4,111)
Fair Value	174,682	168,447
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,059	23,078
Gross Unrealized Gains	6	6
Gross Unrealized Losses	(182)	(254)
Fair Value	22,883	22,830
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	75,289	71,235
Gross Unrealized Gains	131	2
Gross Unrealized Losses	(1,205)	(1,910)
Fair Value	74,215	69,327
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	38,619	37,342
Gross Unrealized Gains	97	62
Gross Unrealized Losses	(822)	(1,142)
Fair Value	37,894	36,262
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,756	40,608
Gross Unrealized Gains	296	225
Gross Unrealized Losses	(362)	(805)
Fair Value	$ 39,690	$ 40,028

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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