Fair Value of Financial Instruments - Estimated Fair Values and Related Carrying or Notional Amounts (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets:
Securities - available-for-sale	$ 174,682	$ 168,447
Reported Value Measurement [Member]
Financial Assets:
Cash and cash equivalents	81,849	38,365
Interest-bearing time deposits	4,509	4,019
Securities - available-for-sale	174,682	168,447
Other securities	5,789	3,679
Loans held for sale	859	495
Loans, net	1,091,829	839,599
Interest receivable	7,238	4,542
Financial Liabilities:
Total Deposits	1,187,424	928,790
Federal funds purchased and securities sold under agreement to repurchase	25,521	32,181
Federal Home Loan Bank advances	24,682
Interest payable	3,728	418
Fair Value [Member]
Financial Assets:
Cash and cash equivalents	81,849	38,365
Interest-bearing time deposits	4,509	3,954
Securities - available-for-sale	174,682	168,447
Other securities	5,789	3,679
Loans held for sale	859	495
Loans, net	1,070,726	823,914
Interest receivable	7,238	4,542
Financial Liabilities:
Total Deposits	1,187,944	928,922
Federal funds purchased and securities sold under agreement to repurchase	25,521	3,181
Federal Home Loan Bank advances	24,604
Interest payable	3,728	418
Interest Bearing Deposits [Member] | Reported Value Measurement [Member]
Financial Liabilities:
Total Deposits	691,648	525,955
Interest Bearing Deposits [Member] | Fair Value [Member]
Financial Liabilities:
Total Deposits	691,702	525,955
Non Interest Bearing Deposits [Member] | Reported Value Measurement [Member]
Financial Liabilities:
Total Deposits	236,847	215,422
Non Interest Bearing Deposits [Member] | Fair Value [Member]
Financial Liabilities:
Total Deposits	236,847	215,422
Time Deposits [Member] | Reported Value Measurement [Member]
Financial Liabilities:
Total Deposits	258,929	187,413
Time Deposits [Member] | Fair Value [Member]
Financial Liabilities:
Total Deposits	259,395	187,545
Level 1 [Member]
Financial Assets:
Cash and cash equivalents	81,849	38,365
Securities - available-for-sale	22,883	36,935
Level 2 [Member]
Financial Assets:
Interest-bearing time deposits	4,509	3,954
Securities - available-for-sale	150,356	130,085
Financial Liabilities:
Total Deposits	236,847	215,422
Level 2 [Member] | Non Interest Bearing Deposits [Member]
Financial Liabilities:
Total Deposits	236,847	215,422
Level 3 [Member]
Financial Assets:
Securities - available-for-sale	1,443	1,427
Other securities	5,789	3,679
Loans held for sale	859	495
Loans, net	1,070,726	823,914
Interest receivable	7,238	4,542
Financial Liabilities:
Total Deposits	951,097	713,500
Federal funds purchased and securities sold under agreement to repurchase	25,521	32,181
Federal Home Loan Bank advances	24,604
Interest payable	3,728	418
Level 3 [Member] | Interest Bearing Deposits [Member]
Financial Liabilities:
Total Deposits	691,702	525,955
Level 3 [Member] | Time Deposits [Member]
Financial Liabilities:
Total Deposits	$ 259,395	$ 187,545