Securities - Components of Held to Maturity Securities Portfolio (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities, Total amortized cost		$ 77,491
Held to maturity securities, Gross unrecognized gains		20
Held to maturity securities, Gross unrecognized losses		(2,436)
Held to maturity securities, Fair value	$ 0	75,075
Mortgage-Backed Securities (MBS) [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities, Total amortized cost		64,442
Held to maturity securities, Gross unrecognized losses		(2,327)
Held to maturity securities, Fair value		62,115
States and Municipalities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities, Total amortized cost		13,049
Held to maturity securities, Gross unrecognized gains		20
Held to maturity securities, Gross unrecognized losses		(109)
Held to maturity securities, Fair value		$ 12,960

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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)
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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