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Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 USD ($)
Participating Interest In Loans, Losses or Charge-offs	$ 0
Allowance for Loan and Lease Losses, Period Increase (Decrease), Total	$ 4,000,000.0
Financing Receivable, Number of Payment Deferrals	750
Financing Receivable, Deferred Payments, Remained Active	$ 3,200,000
Loans and Leases Receivable, Gross, Total	1,069,668,000	$ 802,048,000
Interest and Fee Income, Loans and Leases, Total	46,874,000	26,777,000	$ 20,033,000
Financing Receivable, Deferred Payments	148,000,000
Cash Pass-through Reserve, Federal Home Loan Bank	$ 0	13,231,000
Number of Reportable Segments	1
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total	$ 11,028,000	1,478,000
Retained Earnings (Accumulated Deficit), Ending Balance	37,490,000	$ 28,051,000
Accounting Standards Update 2016-01 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total				$ (244,000)
Retained Earnings (Accumulated Deficit), Ending Balance				$ 244,000
PPP Loans [Member] | SBA CARES Act Paycheck Protection Program [Member]
Financing Receivable, Unamortized Loan Fee	5,000,000.0
Financing Receivable, Unamortized Loan Cost	199,000
Financing Receivable, Unamortized Loan Fee (Cost)	4,800,000
Interest and Fee Income, Loans and Leases, Total	3,000,000.0
Financing Receivable, Amount Forgiven	23,400,000
PPP Loans [Member] | SBA CARES Act Paycheck Protection Program [Member] | Community Shores Bank Corporation [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	$ 37,000,000
Maximum [Member]
Financing Receivable, Number of Payment Deferrals, Remained Active	40
Maximum [Member] | Land Improvements [Member]
Property, Plant and Equipment, Useful Life (Year)	15 years
Maximum [Member] | Building [Member]
Property, Plant and Equipment, Useful Life (Year)	39 years
Maximum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years
Minimum [Member] | Land Improvements [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years
Minimum [Member] | Building [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years
Minimum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life (Year)	3 years
Minimum [Member] | PPP Loans [Member] | SBA CARES Act Paycheck Protection Program [Member]
Loans and Leases Receivable, Gross, Total	$ 126,000,000

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