Note 7 - Securities Available for Sale - Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Less Than Twelve Months # of Investments	39	1
Less Than Twelve Months Fair Value	$ 180,788	$ 4,956
Less Than Twelve Months Unrealized Losses	$ (1,214)	$ (3)
Twelve Months or More # of Investments	2	1
Twelve Months or More Fair Value	$ 4,338	$ 630
Twelve Months or More Unrealized Losses	(107)	(70)
Total fair value	185,126	5,586
Total temporarily impaired securities	$ (1,321)	$ (73)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Less Than Twelve Months # of Investments	16
Less Than Twelve Months Fair Value	$ 72,635
Less Than Twelve Months Unrealized Losses	$ (612)
Twelve Months or More # of Investments	1
Twelve Months or More Fair Value	$ 3,694
Twelve Months or More Unrealized Losses	(51)
Total fair value	76,329
Total temporarily impaired securities	$ (663)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Less Than Twelve Months # of Investments	16
Less Than Twelve Months Fair Value	$ 73,242
Less Than Twelve Months Unrealized Losses	$ (517)
Twelve Months or More # of Investments	0
Twelve Months or More Fair Value	$ 0
Twelve Months or More Unrealized Losses	0
Total fair value	73,242
Total temporarily impaired securities	$ (517)
Collateralized Mortgage Backed Securities [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Less Than Twelve Months # of Investments		1
Less Than Twelve Months Fair Value		$ 4,956
Less Than Twelve Months Unrealized Losses		$ (3)
Twelve Months or More # of Investments		0
Twelve Months or More Fair Value		$ 0
Twelve Months or More Unrealized Losses		0
Total fair value		4,956
Total temporarily impaired securities		$ (3)
Other Marketable Securities [Member] | Preferred Stock [Member]
Less Than Twelve Months # of Investments	0	0
Less Than Twelve Months Fair Value	$ 0	$ 0
Less Than Twelve Months Unrealized Losses	$ 0	$ 0
Twelve Months or More # of Investments	1	1
Twelve Months or More Fair Value	$ 644	$ 630
Twelve Months or More Unrealized Losses	(56)	(70)
Total fair value	644	630
Total temporarily impaired securities	$ (56)	$ (70)
Other Marketable Securities [Member] | US Government Agencies Debt Securities [Member]
Less Than Twelve Months # of Investments	7
Less Than Twelve Months Fair Value	$ 34,911
Less Than Twelve Months Unrealized Losses	$ (85)
Twelve Months or More # of Investments	0
Twelve Months or More Fair Value	$ 0
Twelve Months or More Unrealized Losses	0
Total fair value	34,911
Total temporarily impaired securities	$ (85)