Note 10 - Changes in Accumulated Other Comprehensive Income (Loss) by Component (1) - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended				12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019		Dec. 31, 2019
Balance		$ 255,178	$ 251,358	$ 249,168		$ 245,189		$ 245,189
Unrealized gain (loss) on securities		(801)	366	1,423		3,562
Total other comprehensive income (loss)		(91)	684	2,921		4,403
Total other comprehensive income (loss)		(91)	684	2,921		4,403
Balance		302,938	250,843	302,938		250,843		249,168
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Balance	[1]			(1,275)		(4,736)		(4,736)
Unrealized gain (loss) on securities	[1]			3,483		4,456		4,284
Amounts reclassified from accumulated other comprehensive income to net income (2)	[1],[2]			(2,060)		(894)		(823)
Total other comprehensive income (loss)	[1]			1,423		3,562		3,461
Total change in accumulated other comprehensive income	[1]			1,423		3,562		3,461
Total other comprehensive income (loss)	[1]			1,423		3,562		3,461
Total change in accumulated other comprehensive income	[1]			1,423		3,562		3,461
Balance	[1]	148	(1,174)	148		(1,174)		(1,275)
Accumulated Net Investment Gain (Loss) on Securities Transferred from Available-for-Sale to Held-to-Maturity [Member]
Balance	[1]			(6,066)		(7,191)		(7,191)
Unrealized gain (loss) on securities	[1]			0		0		0
Amounts reclassified from accumulated other comprehensive income to net income (2)	[1],[2]			1,498		841		1,125
Total other comprehensive income (loss)	[1]			1,498		841		1,125
Total change in accumulated other comprehensive income	[1]			1,498		841		1,125
Total other comprehensive income (loss)	[1]			1,498		841		1,125
Total change in accumulated other comprehensive income	[1]			1,498		841		1,125
Balance	[1]	(4,568)	(6,350)	(4,568)		(6,350)		(6,066)
AOCI Attributable to Parent [Member]
Balance		(4,329)	(8,208)	(7,341)	[1]	(11,927)	[1]	(11,927)	[1]
Unrealized gain (loss) on securities	[1]			3,483		4,456		4,284
Amounts reclassified from accumulated other comprehensive income to net income (2)	[1],[2]			(562)		(53)		302
Total other comprehensive income (loss)		(91)	684	2,921	[1]	4,403	[1]	4,586	[1]
Total change in accumulated other comprehensive income	[1]			2,921		4,403		4,586
Total other comprehensive income (loss)		(91)	684	2,921	[1]	4,403	[1]	4,586	[1]
Total change in accumulated other comprehensive income	[1]			2,921		4,403		4,586
Balance	[1]	$ (4,420)	$ (7,524)	$ (4,420)		$ (7,524)		$ (7,341)

[1] All amounts are net of tax. Amounts in parentheses indicate reductions to other comprehensive income.

[2] Reclassification amounts are reported as gains on sales of investment securities, impairment losses, and amortization of net unrealized losses on the Consolidated Statement of Operations.