Note 13 - Regulatory Capital - Required Capital Ratios with Conversion Buffers (Details)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common equity tier 1 capital (CET1)			5.75%	5.125%
Tier 1 capital (to risk weighted assets)			7.25%	6.625%
Total capital (to risk-weighted assets)			9.25%	8.625%
Scenario, Forecast [Member]
Common equity tier 1 capital (CET1)	7.00%	6.375%
Tier 1 capital (to risk weighted assets)	8.50%	7.875%
Total capital (to risk-weighted assets)	10.50%	9.875%