Note 4 - Loans and Allowance for Loan Losses - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Valuation allowance	$ 354		$ 421
Loans with a specific valuation allowance, recorded balance	18,118		19,014
Loans unpaid principal	20,089		20,985
Loans average investment in impaired loans	18,576	$ 10,440
Loans interest income recognized	5	2
Residential Portfolio Segment [Member] | Real Estate Residential, One To Four Family Units [Member]
Loans without a specific valuation allowance, recorded balance	2,457		2,780
Loans without a specific valuation allowance, unpaid principal	2,457		2,780
Loans with a specific valuation allowance, recorded balance	164		330
Loans with a specific valuation allowance, unpaid principal	164		330
Valuation allowance	64		112
Loans with a specific valuation allowance, recorded balance	2,621		3,110
Loans unpaid principal	2,621		3,110
Loans without a specific valuation allowance, average investment in impaired loans	2,680	1,091
Loans without a specific valuation allowance, interest income recognized	0	0
Loans with a specific valuation allowance, average investment in impaired loans	221	1,173
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	2,901	2,264
Loans interest income recognized	0	0
Residential Portfolio Segment [Member] | Real Estate Residential, Multi Family Units [Member]
Loans without a specific valuation allowance, recorded balance	0		0
Loans without a specific valuation allowance, unpaid principal	0		0
Loans with a specific valuation allowance, recorded balance	0		0
Loans with a specific valuation allowance, unpaid principal	0		0
Valuation allowance	0		0
Loans with a specific valuation allowance, recorded balance	0		0
Loans unpaid principal	0		0
Loans without a specific valuation allowance, average investment in impaired loans	0	0
Loans without a specific valuation allowance, interest income recognized	0	0
Loans with a specific valuation allowance, average investment in impaired loans	0	0
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	0	0
Loans interest income recognized	0	0
Residential Portfolio Segment [Member] | Construction Loans [Member]
Loans without a specific valuation allowance, average investment in impaired loans	5,081	0
Loans without a specific valuation allowance, interest income recognized	0	0
Loans with a specific valuation allowance, average investment in impaired loans	965	3,939
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	6,046	3,939
Loans interest income recognized	0	0
Real Estate, Construction [Member]
Loans without a specific valuation allowance, recorded balance	5,081		5,081
Loans without a specific valuation allowance, unpaid principal	5,081		5,081
Loans with a specific valuation allowance, recorded balance	867		1,158
Loans with a specific valuation allowance, unpaid principal	2,838		3,129
Valuation allowance	109		114
Loans with a specific valuation allowance, recorded balance	5,948		6,239
Loans unpaid principal	7,919		8,210
Commercial Real Estate Portfolio Segment [Member]
Loans without a specific valuation allowance, recorded balance	3,340		3,419
Loans without a specific valuation allowance, unpaid principal	3,340		3,419
Loans with a specific valuation allowance, recorded balance	791		801
Loans with a specific valuation allowance, unpaid principal	791		801
Valuation allowance	107		117
Loans with a specific valuation allowance, recorded balance	4,131		4,220
Loans unpaid principal	4,131		4,220
Loans without a specific valuation allowance, average investment in impaired loans	3,391	2,765
Loans without a specific valuation allowance, interest income recognized	2	0
Loans with a specific valuation allowance, average investment in impaired loans	795	281
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	4,186	3,046
Loans interest income recognized	2	0
Commercial Portfolio Segment [Member]
Loans without a specific valuation allowance, recorded balance	4,905		4,902
Loans without a specific valuation allowance, unpaid principal	4,905		4,902
Loans with a specific valuation allowance, recorded balance	322		341
Loans with a specific valuation allowance, unpaid principal	322		341
Valuation allowance	61		63
Loans with a specific valuation allowance, recorded balance	5,227		5,243
Loans unpaid principal	5,227		5,243
Loans without a specific valuation allowance, average investment in impaired loans	4,904	19
Loans without a specific valuation allowance, interest income recognized	0	0
Loans with a specific valuation allowance, average investment in impaired loans	328	904
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	5,232	923
Loans interest income recognized	0	0
Consumer and Other Loans [Member]
Loans without a specific valuation allowance, recorded balance	117		100
Loans without a specific valuation allowance, unpaid principal	117		100
Loans with a specific valuation allowance, recorded balance	74		102
Loans with a specific valuation allowance, unpaid principal	74		102
Valuation allowance	13		15
Loans with a specific valuation allowance, recorded balance	191		202
Loans unpaid principal	191		$ 202
Consumer Portfolio Segment [Member]
Loans without a specific valuation allowance, average investment in impaired loans	105	99
Loans without a specific valuation allowance, interest income recognized	3	2
Loans with a specific valuation allowance, average investment in impaired loans	106	169
Loans with a specific valuation allowance, interest income recognized	0	0
Loans average investment in impaired loans	211	268
Loans interest income recognized	$ 3	$ 2