Note 17 - Regulatory Matters - Risk Based Capital Amounts and Ratios (Details) $ in Thousands		Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Total risk-based capital, actual amount	[1]	$ 457,833	$ 418,460
Total risk-based capital, actual ratio	[1]	0.1379	0.1285
Total risk-based capital, minimum for adequately capitalized amount	[1]	$ 265,548	$ 260,448
Total risk-based capital, minimum for adequately capitalized ratio	[1]	0.0800	0.0800
Common Equity Tier 1 risk-based capital, actual amount		$ 418,460	$ 391,319
Common Equity Tier 1 risk-based capital, actual ratio		0.1261	0.1202
Common Equity Tier 1 risk-based capital, minimum for adequately capitalized amount		$ 149,371	$ 146,502
Common Equity Tier 1 risk-based capital, minimum for adequately capitalized ratio		4.50%	4.50%
Tier 1 risk-based capital, actual amount	[1]	$ 418,460	$ 391,319
Tier 1 risk-based capital, actual ratio	[1]	0.1261	0.1202
Tier 1 risk-based capital, minimum for adequately capitalized amount	[1]	$ 199,161	$ 195,336
Tier 1 risk-based capital, minimum for adequately capitalized ratio	[1]	0.0600	0.0600
Leverage, actual amount	[2]	$ 418,460	$ 391,319
Leverage, actual ratio	[2]	0.0970	0.1060
Leverage, minimum for adequately capitalized amount	[2]	$ 172,571	$ 147,733
Leverage, minimum for adequately capitalized ratio	[2]	0.0400	0.0400
Subsidiaries [Member]
Total risk-based capital, actual amount	[1]	$ 443,406	$ 396,299
Total risk-based capital, actual ratio	[1]	0.1340	0.1220
Total risk-based capital, minimum for adequately capitalized amount	[1]	$ 264,799	$ 259,823
Total risk-based capital, minimum for adequately capitalized ratio	[1]	0.0800	0.0800
Total risk-based capital, minimum for well capitalized amount	[1]	$ 330,999	$ 324,778
Total risk-based capital, minimum for well capitalized ratio	[1]	0.100	0.1000
Common Equity Tier 1 risk-based capital, actual amount		$ 404,033	$ 369,158
Common Equity Tier 1 risk-based capital, actual ratio		0.1221	0.1137
Common Equity Tier 1 risk-based capital, minimum for adequately capitalized amount		$ 148,950	$ 146,150
Common Equity Tier 1 risk-based capital, minimum for adequately capitalized ratio		4.50%	4.50%
Common Equity Tier 1 risk-based capital, minimum for well capitalized amount		$ 215,149	$ 211,106
Common Equity Tier 1 risk-based capital, minimum for well capitalized ratio		6.50%	6.50%
Tier 1 risk-based capital, actual amount	[1]	$ 404,033	$ 369,158
Tier 1 risk-based capital, actual ratio	[1]	0.1221	0.1137
Tier 1 risk-based capital, minimum for adequately capitalized amount	[1]	$ 198,599	$ 194,867
Tier 1 risk-based capital, minimum for adequately capitalized ratio	[1]	0.0600	0.0600
Tier 1 risk-based capital, minimum for well capitalized amount	[1]	$ 264,799	$ 259,823
Tier 1 risk-based capital, minimum for well capitalized ratio	[1]	0.080	0.0800
Leverage, actual amount	[2]	$ 404,033	$ 369,158
Leverage, actual ratio	[2]	0.0938	0.1067
Leverage, minimum for adequately capitalized amount	[2]	$ 172,316	$ 138,392
Leverage, minimum for adequately capitalized ratio	[2]	0.0400	0.0400
Leverage, minimum for well capitalized amount	[2]	$ 215,394	$ 172,990
Leverage, minimum for well capitalized ratio	[2]	0.050	0.0500

[1] Ratio is computed in relation to risk-weighted assets.

[2] Ratio is computed in relation to average assets.