Note 5 - Loans and Allowance for Loan Losses - Impaired Loans (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Impaired loans with no related allowance recorded, carrying amount	$ 2,238
Impaired loans with no related allowance recorded, unpaid principal balance	2,238
Impaired loans with an allowance recorded, carrying amount	842	791
Impaired loans with an allowance recorded, unpaid principal balance	842	791
Impaired loans, related allowances	178	98
Impaired loans, carrying amount	3,080	791
Impaired loans, unpaid principal balance	3,080	791
Impaired loans, average recorded investment	1,020	1,688
Impaired loans, interest income recognized	37	55
Impaired loans, interest income received	40	54
Real Estate [Member]
Impaired loans, average recorded investment		59
Impaired loans, interest income recognized		7
Impaired loans, interest income received		5
Real Estate [Member] \| Construction, Land Development and Other Land Loans [Member]
Impaired loans with no related allowance recorded, carrying amount	73
Impaired loans with no related allowance recorded, unpaid principal balance	73
Impaired loans with an allowance recorded, carrying amount	155
Impaired loans with an allowance recorded, unpaid principal balance	155
Impaired loans, related allowances	31
Impaired loans, carrying amount	228
Impaired loans, unpaid principal balance	228
Impaired loans, average recorded investment	52	902
Impaired loans, interest income recognized	6
Impaired loans, interest income received	6
Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member]
Impaired loans with no related allowance recorded, carrying amount	2,150
Impaired loans with no related allowance recorded, unpaid principal balance	2,150
Impaired loans with an allowance recorded, carrying amount	58	187
Impaired loans with an allowance recorded, unpaid principal balance	58	187
Impaired loans, related allowances	51	5
Impaired loans, carrying amount	2,208	187
Impaired loans, unpaid principal balance	2,208	187
Impaired loans, average recorded investment	370	190
Impaired loans, interest income recognized	1	13
Impaired loans, interest income received	1	14
Real Estate [Member] \| Secured by Multi-family Residential Properties [Member]
Impaired loans with no related allowance recorded, carrying amount
Impaired loans with no related allowance recorded, unpaid principal balance
Impaired loans with an allowance recorded, carrying amount
Impaired loans with an allowance recorded, unpaid principal balance
Impaired loans, related allowances
Impaired loans, carrying amount
Impaired loans, unpaid principal balance
Impaired loans, average recorded investment
Impaired loans, interest income recognized
Impaired loans, interest income received
Real Estate [Member] \| Secured by Non-farm, Non-residential Properties [Member]
Impaired loans with no related allowance recorded, carrying amount	8
Impaired loans with no related allowance recorded, unpaid principal balance	8
Impaired loans with an allowance recorded, carrying amount	517	532
Impaired loans with an allowance recorded, unpaid principal balance	517	532
Impaired loans, related allowances	7	21
Impaired loans, carrying amount	525	532
Impaired loans, unpaid principal balance	525	532
Impaired loans, average recorded investment	524	537
Impaired loans, interest income recognized	25	35
Impaired loans, interest income received	27	35
Real Estate [Member] \| Other Real Estate Loans [Member]
Impaired loans with no related allowance recorded, carrying amount	7
Impaired loans with no related allowance recorded, unpaid principal balance	7
Impaired loans with an allowance recorded, carrying amount
Impaired loans with an allowance recorded, unpaid principal balance
Impaired loans, related allowances
Impaired loans, carrying amount	7
Impaired loans, unpaid principal balance	7
Impaired loans, average recorded investment	1
Impaired loans, interest income recognized
Impaired loans, interest income received
Commercial and Industrial Loans [Member]
Impaired loans with no related allowance recorded, carrying amount
Impaired loans with no related allowance recorded, unpaid principal balance
Impaired loans with an allowance recorded, carrying amount	67	72
Impaired loans with an allowance recorded, unpaid principal balance	67	72
Impaired loans, related allowances	67	72
Impaired loans, carrying amount	67	72
Impaired loans, unpaid principal balance	67	$ 72
Impaired loans, average recorded investment	68
Impaired loans, interest income recognized	3
Impaired loans, interest income received	4
Consumer Portfolio Segment [Member]
Impaired loans with no related allowance recorded, carrying amount
Impaired loans with no related allowance recorded, unpaid principal balance
Impaired loans with an allowance recorded, carrying amount	45
Impaired loans with an allowance recorded, unpaid principal balance	45
Impaired loans, related allowances	22
Impaired loans, carrying amount	45
Impaired loans, unpaid principal balance	45
Impaired loans, average recorded investment	5
Impaired loans, interest income recognized	2
Impaired loans, interest income received	$ 2

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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