Note 7 - Fair Value Measurements - Level 3 Fair Value Measurements (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Impaired loans [Member] | Present Value of Cash Flows [Member] | Minimum [Member]
Discount rate	5.50%	6.75%
Impaired loans [Member] | Present Value of Cash Flows [Member] | Maximum [Member]
Discount rate	13.25%	8.00%
Impaired loans [Member] | Present Value of Cash Flows [Member] | Weighted Average [Member]
Discount rate	6.01%	7.35%
Other Real Estate Owned [Member] | Discounted Appraised Value [Member] | Minimum [Member]
Discount rate	1.68%	0.00%
Selling cost	2.44%	2.91%
Other Real Estate Owned [Member] | Discounted Appraised Value [Member] | Maximum [Member]
Discount rate	60.94%	53.46%
Selling cost	11.09%	8.60%
Other Real Estate Owned [Member] | Discounted Appraised Value [Member] | Weighted Average [Member]
Discount rate	10.34%	13.66%
Selling cost	4.86%	6.48%