Fair Value Measurements and Disclosure - Fair Value Estimates (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Financial Assets:
Investment securities	$ 0	$ 0
Quoted Prices In Active Markets for Identical Assets Level 1
Financial Assets:
Cash and cash equivalents	309,460,000	220,337,000
Investment securities	3,769,000	3,659,000
Loans	0	0
Accrued interest receivable	0	0
Deposits:
Noninterest-bearing	304,172,000	292,720,000
NOW and money market	404,416,000	340,445,000
Savings	92,274,000	90,046,000
Time deposits	0	0
Total deposits	800,862,000	723,211,000
Junior subordinated debt	0	0
Accrued interest payable	0	0
Significant Other Observable Inputs Level 2
Financial Assets:
Cash and cash equivalents	0	0
Investment securities	59,863,000	66,426,000
Loans	0	0
Accrued interest receivable	10,314,000	8,341,000
Deposits:
Noninterest-bearing	0	0
NOW and money market	0	0
Savings	0	0
Time deposits	0	0
Total deposits	0	0
Junior subordinated debt	0	0
Accrued interest payable	77,000	57,000
Significant Unobservable Inputs Level 3
Financial Assets:
Cash and cash equivalents	0	0
Investment securities	0	0
Loans	552,173,000	566,195,000
Accrued interest receivable	0	0
Deposits:
Noninterest-bearing	0	0
NOW and money market	0	0
Savings	0	0
Time deposits	69,735,000	81,745,000
Total deposits	69,735,000	81,745,000
Junior subordinated debt	10,496,000	10,155,000
Accrued interest payable	0	0
Carrying Amount
Financial Assets:
Cash and cash equivalents	309,460,000	220,337,000
Investment securities	63,632,000	70,085,000
Loans	564,358,000	579,419,000
Accrued interest receivable	10,314,000	8,341,000
Deposits:
Noninterest-bearing	304,172,000	292,720,000
NOW and money market	404,416,000	340,445,000
Savings	92,274,000	90,046,000
Time deposits	70,053,000	82,432,000
Total deposits	870,915,000	805,643,000
Junior subordinated debt	10,496,000	10,155,000
Accrued interest payable	77,000	57,000
Estimated Fair Value
Financial Assets:
Cash and cash equivalents	309,460,000	220,337,000
Investment securities	59,863,000	70,085,000
Loans	552,173,000	566,195,000
Accrued interest receivable	10,314,000	8,341,000
Deposits:
Noninterest-bearing	304,172,000	292,720,000
NOW and money market	404,416,000	340,445,000
Savings	92,274,000	90,046,000
Time deposits	69,735,000	81,745,000
Total deposits	870,597,000	804,956,000
Junior subordinated debt	10,496,000	10,155,000
Accrued interest payable	$ 77,000	$ 57,000