Note 13 - Fair Value Disclosures - Estimated Fair Value and Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	$ 13,436	$ 11,201
Federal Home Loan Bank stock	5,384	5,011
Federal Reserve Bank stock	2,526	2,033
Loans receivable, net	747,290	603,361
Accrued interest and dividends receivable	4,903	3,479
Mortgage servicing rights	8,672	8,670
Financial liabilities:
Non-maturing interest bearing deposits	357,546	321,399
Noninterest bearing deposits	183,116	142,788
Time certificates of deposit	207,207	160,735
Accrued expenses and other liabilities	11,987	5,388
Federal Home Loan Bank advances and other borrowings	106,801	101,885
Other long-term debt	24,672	24,002
Reported Value Measurement [Member]
Financial assets:
Cash and cash equivalents	13,436	11,201
Federal Home Loan Bank stock	5,384	5,011
Federal Reserve Bank stock	2,526	2,033
Loans receivable, net	744,684	608,043
Accrued interest and dividends receivable	4,903	3,479
Mortgage servicing rights	7,666	7,100
Financial liabilities:
Non-maturing interest bearing deposits	357,546	321,399
Noninterest bearing deposits	183,116	142,788
Time certificates of deposit	207,726	162,424
Accrued expenses and other liabilities	11,987	5,388
Federal Home Loan Bank advances and other borrowings	106,748	102,222
Other long-term debt	25,155	25,155
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	13,436	11,201
Federal Home Loan Bank stock	5,384	5,011
Federal Reserve Bank stock	2,526	2,033
Loans receivable, net	0	0
Accrued interest and dividends receivable	4,903	3,479
Mortgage servicing rights	0	0
Financial liabilities:
Non-maturing interest bearing deposits	0	0
Noninterest bearing deposits	183,116	142,788
Time certificates of deposit	0	0
Accrued expenses and other liabilities	11,987	5,388
Federal Home Loan Bank advances and other borrowings	0	0
Other long-term debt	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	0	0
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Loans receivable, net	0	0
Accrued interest and dividends receivable	0	0
Mortgage servicing rights	0	0
Financial liabilities:
Non-maturing interest bearing deposits	357,546	321,399
Noninterest bearing deposits	0	0
Time certificates of deposit	0	0
Accrued expenses and other liabilities	0	0
Federal Home Loan Bank advances and other borrowings	0	0
Other long-term debt	0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	0	0
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Loans receivable, net	747,290	603,361
Accrued interest and dividends receivable	0	0
Mortgage servicing rights	8,672	8,670
Financial liabilities:
Non-maturing interest bearing deposits	0	0
Noninterest bearing deposits	0	0
Time certificates of deposit	207,207	160,735
Accrued expenses and other liabilities	0	0
Federal Home Loan Bank advances and other borrowings	106,801	101,885
Other long-term debt	$ 24,672	$ 24,002