Disclosures About Fair Value of Financial Instruments - Summary of estimated fair values, and related carrying amounts of financial instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financial Assets
Cash and short-term investments	$ 22,318	$ 15,026	$ 13,458	$ 10,319
Federal funds sold	285	546
Investment securities	142,712	58,750
Loans held for sale	80,255	29,233
Net loans held for investment	456,474	411,288
Accrued interest receivable	2,162	1,769
Bank-owned life insurance	8,871	8,455
Financial Liabilities
Deposits	520,280	415,027
Other borrowed funds	129,600	73,100
Subordinated debt, net	9,792	9,766
Accrued interest payable	834	395
Financial Assets
Cash and short-term investments	22,318	15,026
Federal funds sold	285	546
Investment securities	143,210	58,688
Loans held for sale	80,255	29,233
Net loans held for investment	462,414	404,888
Accrued interest receivable	2,162	1,769
Bank-owned life insurance	8,871	8,455
Financial Liabilities
Deposits	514,070	404,350
Other borrowed funds	129,908	73,113
Subordinated debt, net	9,792	9,766
Accrued interest payable	834	395
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and short-term investments	22,318	15,026
Federal funds sold	285	546
Significant Observable Inputs (Level 2) [Member]
Financial Assets
Investment securities	143,210	58,688
Loans held for sale	80,255	29,233
Accrued interest receivable	2,162	1,769
Bank-owned life insurance	8,871	8,455
Financial Liabilities
Deposits	428,908	323,280
Other borrowed funds	129,908	73,113
Accrued interest payable	834	395
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Net loans held for investment	462,414	404,888
Financial Liabilities
Deposits	85,162	81,070
Subordinated debt, net	$ 9,792	$ 9,766

Accrued interest receivable.

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Accrued interest receivable fair value disclosure.

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Bank owned life insurance fair value disclosure.

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Federal funds sold fair value disclosure.

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Loans held for sale.

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Loans held to maturity fair value disclosure.

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Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities.

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-Name Accounting Standards Codification
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-Section S99
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Fair value portion of accrued expenses.

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The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The amount outstanding of funds lent to other depository institutions, securities brokers, or securities dealers in the form of Federal Funds sold; for example, immediately available funds lent under agreements or contracts that mature in one business day or roll over under a continuing contract, regardless of the nature of the transaction or the collateral involved, excluding overnight lending for commercial and industrial purposes. Also include Federal Funds sold under agreements to resell on a gross basis, excluding (1) sales of term Federal Funds, (2) due bills representing purchases of securities or other assets by the reporting bank that have not yet been delivered and similar instruments, (3) resale agreements that mature in more than one business day involving assets other than securities, and (4) yield maintenance dollar repurchase agreements.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Sum of the carrying amounts as of the balance sheet date of all investments.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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