Securities - Additional Information (Detail)	3 Months Ended	9 Months Ended
Sep. 30, 2021 USD ($) Security	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Security	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Investments Debt And Equity Securities [Abstract]
Fair value of pledged securities	$ 119,900,000		$ 119,900,000		$ 91,000,000.0
Restricted stock investment in FHLB stock	4,100,000		4,100,000		4,100,000
Federal Reserve Bank stock	471,000		471,000		$ 471,000
Proceeds from sale of available-for-sale securities	$ 0	$ 0	$ 0	$ 0
Number of securities in an unrealized loss position, Total \| Security	57		57
Number of securities in continuous unrealized loss position, 12 months or more \| Security			7

Number Of Securities In Unrealized Loss Position

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- Definition

Number Of Securities In Unrealized Loss Position For Period Of One Year Or Greater

+ References

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
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Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

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- References

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 12
-Subparagraph (a)
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- Definition

Fair value of the securities pledged as collateral against securities loaned.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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