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			9 Months Ended			12 Months Ended
		Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018		Dec. 31, 2017
Beginning Balance					$ 11,220		$ 8,765	$ 8,765
Charge-offs					(1,635)			(472)
Recoveries					91			537
Provision		$ 479		$ 503	2,414		1,451	2,390
Ending Balance		12,090			12,090			11,220
Allowance for credit losses, individually evaluated for impairment		674			674			1,280
Allowance for credit losses, collectively evaluated for impairment		11,416			11,416			9,940
Allowance for credit losses, purchased credit impaired	[1]
Loans receivable		1,694,727			1,694,727			1,528,469
Loans receivable, individually evaluated for impairment		12,226			12,226			12,360
Loans receivable, collectively evaluated for impairment		1,674,984			1,674,984			1,505,405
Loans receivable, purchased credit impaired		7,517	[1]		7,517	[1]		10,704	[1]	$ 696
Commercial Real Estate Portfolio Segment [Member] | Construction and Land [Member]
Beginning Balance					1,590		1,421	1,421
Charge-offs					(2)			(90)
Recoveries								398
Provision					(111)			(139)
Ending Balance		1,477			1,477			1,590
Allowance for credit losses, individually evaluated for impairment
Allowance for credit losses, collectively evaluated for impairment		1,477			1,477			1,590
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		220,524			220,524			211,054
Loans receivable, individually evaluated for impairment		399			399			32
Loans receivable, collectively evaluated for impairment		220,125			220,125			211,022
Loans receivable, purchased credit impaired	[1]
Commercial Real Estate Portfolio Segment [Member] | Farmland [Member]
Beginning Balance					104		76	76
Charge-offs					(2)			0
Recoveries					0			0
Provision					84			28
Ending Balance		186			186			104
Allowance for credit losses, individually evaluated for impairment		4			4			0
Allowance for credit losses, collectively evaluated for impairment		182			182			104
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		45,809			45,809			45,989
Loans receivable, individually evaluated for impairment		186			186			112
Loans receivable, collectively evaluated for impairment		45,390			45,390			45,713
Loans receivable, purchased credit impaired	[1]	233			233			164
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Beginning Balance					2,715		2,323	2,323
Charge-offs					(10)
Recoveries								13
Provision					1,299			379
Ending Balance		4,004			4,004			2,715
Allowance for credit losses, individually evaluated for impairment		46			46			47
Allowance for credit losses, collectively evaluated for impairment		3,958			3,958			2,668
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		620,427			620,427			518,660
Loans receivable, individually evaluated for impairment		4,078			4,078			4,155
Loans receivable, collectively evaluated for impairment		609,408			609,408			507,506
Loans receivable, purchased credit impaired	[1]	6,941			6,941			6,999
Residential Portfolio Segment [Member] | Real Estate Residential One- to Four-Family [Member]
Beginning Balance					1,538		1,284	1,284
Charge-offs					(54)			(294)
Recoveries					12			18
Provision					321			530
Ending Balance		1,817			1,817			1,538
Allowance for credit losses, individually evaluated for impairment		122			122			96
Allowance for credit losses, collectively evaluated for impairment		1,695			1,695			1,442
Allowance for credit losses, purchased credit impaired	[1]
Loans receivable		281,413			281,413			270,583
Loans receivable, individually evaluated for impairment		2,567			2,567			2,728
Loans receivable, collectively evaluated for impairment		278,779			278,779			267,761
Loans receivable, purchased credit impaired	[1]	67			67			94
Residential Portfolio Segment [Member] | Multi-family Residential [Member]
Beginning Balance					236		144	144
Charge-offs					0			0
Recoveries					0			0
Provision					(46)			92
Ending Balance		190			190			236
Allowance for credit losses, individually evaluated for impairment		0			0			0
Allowance for credit losses, collectively evaluated for impairment		190			190			236
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		31,448			31,448			39,273
Loans receivable, individually evaluated for impairment		0			0			0
Loans receivable, collectively evaluated for impairment		31,448			31,448			39,273
Loans receivable, purchased credit impaired	[1]	0			0			0
Commercial Portfolio Segment [Member]
Beginning Balance					4,453		3,147	3,147
Charge-offs					(1,544)
Recoveries					37			28
Provision					802			1,278
Ending Balance		3,748			3,748			4,453
Allowance for credit losses, individually evaluated for impairment		401			401			1,112
Allowance for credit losses, collectively evaluated for impairment		3,347			3,347			3,341
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		415,163			415,163			363,640
Loans receivable, individually evaluated for impairment		4,607			4,607			5,208
Loans receivable, collectively evaluated for impairment		410,280			410,280			354,985
Loans receivable, purchased credit impaired	[1]	276			276			3,447
Consumer Portfolio Segment [Member]
Beginning Balance					584		$ 370	370
Charge-offs					(23)			(88)
Recoveries					42			80
Provision					65			222
Ending Balance		668			668			584
Allowance for credit losses, individually evaluated for impairment		101			101			25
Allowance for credit losses, collectively evaluated for impairment		567			567			559
Allowance for credit losses, purchased credit impaired	[1]	0			0			0
Loans receivable		79,943			79,943			79,270
Loans receivable, individually evaluated for impairment		389			389			125
Loans receivable, collectively evaluated for impairment		79,554			79,554			79,145
Loans receivable, purchased credit impaired	[1]	$ 0			$ 0			$ 0

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