Note 18 - Regulatory Matters - Transition Schedule for New Ratios, Including the Capital Conservation Buffer (Details)	Dec. 31, 2017	Dec. 31, 2016
Minimum common equity tier 1 capital ratio	4.50%	4.50%
Minimum tier 1 capital ratio	6.00%	6.00%
Minimum total capital ratio	8.00%	8.00%
Phased in Beginning 2017 [Member]
Minimum common equity tier 1 capital ratio	4.50%
Common equity tier 1 capital conservation buffer	1.25%
Minimum common equity tier 1 capital ratio plus capital conservation buffer	5.75%
Phase-in of most deductions from common equity tier 1 capital	80.00%
Minimum tier 1 capital ratio	6.00%
Minimum tier 1 capital ratio plus capital conservation buffer	7.25%
Minimum total capital ratio	8.00%
Minimum total capital ratio plus capital conservation buffer	9.25%
Phased in Beginning 2018 [Member]
Minimum common equity tier 1 capital ratio	4.50%
Common equity tier 1 capital conservation buffer	1.875%
Minimum common equity tier 1 capital ratio plus capital conservation buffer	6.375%
Phase-in of most deductions from common equity tier 1 capital	100.00%
Minimum tier 1 capital ratio	6.00%
Minimum tier 1 capital ratio plus capital conservation buffer	7.875%
Minimum total capital ratio	8.00%
Minimum total capital ratio plus capital conservation buffer	9.875%
Phased in Beginning 2019 [Member]
Minimum common equity tier 1 capital ratio	4.50%
Common equity tier 1 capital conservation buffer	2.50%
Minimum common equity tier 1 capital ratio plus capital conservation buffer	7.00%
Phase-in of most deductions from common equity tier 1 capital	100.00%
Minimum tier 1 capital ratio	6.00%
Minimum tier 1 capital ratio plus capital conservation buffer	8.50%
Minimum total capital ratio	8.00%
Minimum total capital ratio plus capital conservation buffer	10.50%