Note 6 - Loans and the Allowance for Loan Losses - Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans	$ 1,586,182	$ 1,528,469
Allowance for loan losses	(11,818)	(11,220)	$ (8,765)
Net loans	1,574,364	1,517,249
Commercial Real Estate Portfolio Segment [Member] \| Construction and Land [Member]
Loans	211,888	211,054
Allowance for loan losses	(1,600)	(1,590)	(1,421)
Commercial Real Estate Portfolio Segment [Member] \| Farmland [Member]
Loans	44,066	45,989
Allowance for loan losses	(105)	(104)	(76)
Commercial Real Estate Portfolio Segment [Member] \| Nonfarm Nonresidential [Member]
Loans	550,103	518,660
Allowance for loan losses	(2,849)	(2,715)	(2,323)
Residential Portfolio Segment [Member] \| Real Estate Residential One- to Four-Family [Member]
Loans	275,610	270,583
Allowance for loan losses	(1,574)	(1,538)	(1,284)
Residential Portfolio Segment [Member] \| Multi-family Residential [Member]
Loans	39,548	39,273
Allowance for loan losses	(235)	(236)	(144)
Commercial Portfolio Segment [Member]
Loans	389,855	363,640
Allowance for loan losses	(4,886)	(4,453)	(3,147)
Consumer Portfolio Segment [Member]
Loans	75,112	79,270
Allowance for loan losses	$ (569)	$ (584)	$ (370)

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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