Note 13 - Fair Value Measurements - Assets Measured At Fair Value On a Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Collateral-dependent impaired loans, fair value	$ 5,434	$ 8,885
OREO, fair value	1,074	4,446
Fair Value, Inputs, Level 1 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value	0	0
Fair Value, Inputs, Level 2 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Collateral-dependent impaired loans, fair value	5,434	8,885
OREO, fair value	1,074	4,446
Real Estate Portfolio Segment [Member] | Real Estate Construction and Land Development [Member]
Collateral-dependent impaired loans, fair value	1,271	1,553
OREO, fair value	1,074	3,468
Real Estate Portfolio Segment [Member] | Real Estate Construction and Land Development [Member] | Fair Value, Inputs, Level 1 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value	0	0
Real Estate Portfolio Segment [Member] | Real Estate Construction and Land Development [Member] | Fair Value, Inputs, Level 2 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value	0	0
Real Estate Portfolio Segment [Member] | Real Estate Construction and Land Development [Member] | Fair Value, Inputs, Level 3 [Member]
Collateral-dependent impaired loans, fair value	1,271	1,553
OREO, fair value	1,074	3,468
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Residential [Member]
Collateral-dependent impaired loans, fair value	4,163	4,687
OREO, fair value		157
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Residential [Member] | Fair Value, Inputs, Level 1 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value		0
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Residential [Member] | Fair Value, Inputs, Level 2 [Member]
Collateral-dependent impaired loans, fair value	0	0
OREO, fair value		0
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Residential [Member] | Fair Value, Inputs, Level 3 [Member]
Collateral-dependent impaired loans, fair value	$ 4,163	4,687
OREO, fair value		157
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Farmland and Other Commercial Enterprises [Member]
Collateral-dependent impaired loans, fair value		2,645
OREO, fair value		821
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Farmland and Other Commercial Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Collateral-dependent impaired loans, fair value		0
OREO, fair value		0
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Farmland and Other Commercial Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Collateral-dependent impaired loans, fair value		0
OREO, fair value		0
Real Estate Portfolio Segment [Member] | Real Estate Mortgage Farmland and Other Commercial Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Collateral-dependent impaired loans, fair value		2,645
OREO, fair value		$ 821