Note 13 - Fair Value Measurements - Quantitative Information About Unobservable Inputs for Assets Measured on a Nonrecurring Basis Using Level 3 Measurements (Details) - Fair Value, Inputs, Level 3 [Member] - Valuation, Market Approach [Member] $ in Thousands	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Collateral-dependent impaired loans, fair value	$ 5,447	$ 8,885
OREO, fair value	$ 160	$ 4,446
Minimum [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Collateral-dependent impaired loans, measurement input	0	0
OREO, measurement input	0	0
Maximum [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Collateral-dependent impaired loans, measurement input	73.6	22.8
OREO, measurement input	35.9	71.7
Weighted Average [Member] | Measurement Input, Discount for Lack of Marketability [Member]
Collateral-dependent impaired loans, measurement input	1.3	3.1
OREO, measurement input	10.8	4