Note 11 - Fair Value of Financial Instruments and Fair Value Measurements - Quantitative Information for Financial Instruments Measured at Fair Value (Details) $ in Thousands	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Other Real Estate Owned, fair value	$ 987	$ 1,841	$ 4,256
Fair Value, Nonrecurring [Member]
Impaired loans, fair value	2,679	3,352
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value	$ 2,679	3,352
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Cost to Sell [Member]
Other Real Estate Owned, measurement input	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Cost to Sell [Member]
Other Real Estate Owned, measurement input	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Cost to Sell [Member]
Other Real Estate Owned, measurement input	0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Other Real Estate Owned, fair value	$ 714	$ 1,183
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Other Real Estate Owned, measurement input	(30)	(30)
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Other Real Estate Owned, measurement input	9.82	9.82
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Other Real Estate Owned, measurement input	25.02	25.02
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Other Real Estate Owned, measurement input	99.39	99.39
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Other Real Estate Owned, measurement input	(2.49)	(2.49)
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Other Real Estate Owned, measurement input	40.36	35.26
Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Cap Rate [Member]
Other Real Estate Owned, measurement input		10
Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Discount Rate [Member]
Other Real Estate Owned, measurement input	10
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value	$ 218	$ 213
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	(10.86)	(10.86)
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	0	0
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	6.7	6.7
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	25	25
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	(2.08)	(2.08)
Real Estate Portfolio Segment [Member] | Residential [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	12.5	12.5
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value		$ 360
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		(6)
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		0
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		1,975
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		10
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		984.2
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		5
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		0
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		35
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	(37.25)
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		17.5
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value	$ 2,134	$ 2,415
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		(60)
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	0
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Cap Rate [Member]
Impaired loans, measurement input	7.75
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		80
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	10
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Cap Rate [Member]
Impaired loans, measurement input	10.5
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		10
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	5
Real Estate Portfolio Segment [Member] | Commercial [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Cap Rate [Member]
Impaired loans, measurement input	9.13	10.13
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value	$ 327	$ 328
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	(71)	(71)
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	10	10
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input	(3.5)	(3.5)
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	80	80
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired loans, measurement input		(37.25)
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		45
Real Estate Portfolio Segment [Member] | Farmland [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input	45
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Impaired loans, fair value		$ 36
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Minimum [Member] | Measurement Input, Cost to Sell [Member]
Impaired loans, measurement input		0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Appraised Value [Member]
Impaired loans, measurement input		15
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Maximum [Member] | Measurement Input, Cost to Sell [Member]
Impaired loans, measurement input		0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Cap Rate [Member]
Impaired loans, measurement input		15
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Weighted Average [Member] | Measurement Input, Cost to Sell [Member]
Impaired loans, measurement input		0