Note 6 - Loans and the Allowance for Loan Losses - Allowance for Credit Losses and Recorded Investment in Loans Receivable (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017	Dec. 31, 2017		Dec. 31, 2016
Beginning Balance					$ 8,765		$ 8,162	$ 8,162
Charge-offs					(420)			(3,784)
Recoveries					463			150
Provision		$ 474		$ 1,305	948		1,660	4,237
Ending Balance		9,756			9,756			8,765
Allowance for credit losses, individually evaluated for impairment		375			375			536
Allowance for credit losses, collectively evaluated for impairment		9,347			9,347			8,195
Allowance for credit losses, purchased credit impaired	[1]	34			34			34
Loans receivable		1,234,031			1,234,031			975,284
Loans receivable, individually evaluated for impairment		17,488			17,488			13,449
Loans receivable, collectively evaluated for impairment		1,211,112			1,211,112			961,139
Loans receivable, purchased credit impaired		5,431	[1]		5,431	[1]		696	[1]	$ 1,776
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member]
Beginning Balance					1,421		933	933
Charge-offs					(90)			(2)
Recoveries					398			1
Provision					24			489
Ending Balance		1,753			1,753			1,421
Allowance for credit losses, individually evaluated for impairment		0			0			36
Allowance for credit losses, collectively evaluated for impairment		1,753			1,753			1,385
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		204,099			204,099			143,535
Loans receivable, individually evaluated for impairment		9			9			92
Loans receivable, collectively evaluated for impairment		204,090			204,090			143,443
Loans receivable, purchased credit impaired	[1]	0			0			0
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member]
Beginning Balance					76		75	75
Charge-offs					0			0
Recoveries					0			0
Provision					1			1
Ending Balance		77			77			76
Allowance for credit losses, individually evaluated for impairment		0			0			0
Allowance for credit losses, collectively evaluated for impairment		77			77			76
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		15,173			15,173			10,480
Loans receivable, individually evaluated for impairment		0			0			0
Loans receivable, collectively evaluated for impairment		15,173			15,173			10,480
Loans receivable, purchased credit impaired	[1]	0			0			0
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Beginning Balance					2,323		2,314	2,314
Charge-offs					0			(617)
Recoveries					0			23
Provision					24			603
Ending Balance		2,347			2,347			2,323
Allowance for credit losses, individually evaluated for impairment		46			46			46
Allowance for credit losses, collectively evaluated for impairment		2,301			2,301			2,277
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		399,166			399,166			337,699
Loans receivable, individually evaluated for impairment		8,329			8,329			5,831
Loans receivable, collectively evaluated for impairment		385,610			385,610			331,380
Loans receivable, purchased credit impaired	[1]	5,227			5,227			488
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member]
Beginning Balance					1,284		1,228	1,228
Charge-offs					(265)			(184)
Recoveries					8			48
Provision					435			192
Ending Balance		1,462			1,462			1,284
Allowance for credit losses, individually evaluated for impairment		102			102			125
Allowance for credit losses, collectively evaluated for impairment		1,326			1,326			1,125
Allowance for credit losses, purchased credit impaired	[1]	34			34			34
Loans receivable		224,986			224,986			157,505
Loans receivable, individually evaluated for impairment		2,928			2,928			2,817
Loans receivable, collectively evaluated for impairment		221,854			221,854			154,480
Loans receivable, purchased credit impaired	[1]	204			204			208
Residential Portfolio Segment [Member] | Multi-family Residential [Member]
Beginning Balance					144		172	172
Charge-offs					0			0
Recoveries					0			0
Provision					11			(28)
Ending Balance		155			155			144
Allowance for credit losses, individually evaluated for impairment		0			0			0
Allowance for credit losses, collectively evaluated for impairment		155			155			144
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		22,511			22,511			20,717
Loans receivable, individually evaluated for impairment		0			0			0
Loans receivable, collectively evaluated for impairment		22,511			22,511			20,717
Loans receivable, purchased credit impaired	[1]	0			0			0
Commercial Portfolio Segment [Member]
Beginning Balance					3,147		3,039	3,039
Charge-offs					0			(2,945)
Recoveries					13			40
Provision					363			3,013
Ending Balance		3,523			3,523			3,147
Allowance for credit losses, individually evaluated for impairment		227			227			329
Allowance for credit losses, collectively evaluated for impairment		3,296			3,296			2,818
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		298,967			298,967			254,427
Loans receivable, individually evaluated for impairment		5,889			5,889			4,268
Loans receivable, collectively evaluated for impairment		293,078			293,078			250,159
Loans receivable, purchased credit impaired	[1]	0			0			0
Consumer Portfolio Segment [Member]
Beginning Balance					370		$ 401	401
Charge-offs					(65)			(36)
Recoveries					44			38
Provision					90			(33)
Ending Balance		439			439			370
Allowance for credit losses, individually evaluated for impairment		0			0			0
Allowance for credit losses, collectively evaluated for impairment		439			439			370
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		69,129			69,129			50,921
Loans receivable, individually evaluated for impairment		333			333			441
Loans receivable, collectively evaluated for impairment		68,796			68,796			50,480
Loans receivable, purchased credit impaired	[1]	$ 0			$ 0			$ 0

[1] Purchased credit impaired loans are evaluated for impairment on an individual basis.