Fair Value - Summary of Carrying Value and Fair Values of the Bank's Financial Instruments (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Securities available-for-sale	$ 187,469,000	$ 192,621,000
Securities held to maturity, fair value	3,766,000	3,848,000
Loans held for sale	0	0
Carrying amount
Financial assets:
Restricted equity securities	8,817,000	8,806,000
Carrying amount | Level 1
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	49,842,000	78,078,000
Federal funds sold	2,747,000	4,719,000
Carrying amount | Level 2
Financial assets:
Securities available-for-sale	187,469,000	192,621,000
Securities held to maturity, fair value	3,740,000	3,759,000
Loans held for sale	50,499,000	74,093,000
Accrued interest receivable	4,430,000	4,084,000
Other assets	23,519,000	22,663,000
Financial liabilities:
Federal Home Loan Bank advances	125,000,000	70,000,000
Carrying amount | Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net	1,073,870,000	947,537,000
Financial liabilities:
Deposits	1,126,403,000	1,119,866,000
Other liabilities	2,447,000	3,672,000
Fair value | Level 1
Financial assets:
Cash and due from banks, interest-bearing deposits in financial institutions	49,842,000	78,078,000
Federal funds sold	2,747,000	4,719,000
Fair value | Level 2
Financial assets:
Securities available-for-sale	187,469,000	192,621,000
Securities held to maturity, fair value	3,766,000	3,848,000
Loans held for sale	51,326,000	75,549,000
Accrued interest receivable	4,430,000	4,084,000
Other assets	23,519,000	22,663,000
Financial liabilities:
Federal Home Loan Bank advances	124,983,000	69,980,000
Fair value | Significant Unobservable Inputs (Level 3)
Financial assets:
Loans, net	1,065,226,000	944,037,000
Financial liabilities:
Deposits	1,074,725,000	1,065,669,000
Other liabilities	$ 2,447,000	$ 3,672,000