Note 5 - Loans - Loans Individually Evaluated for Impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loans with no related allowance recorded, recorded investment	$ 7,332	$ 3,609
Loans with no related allowance recorded, unpaid principal balance	9,072	4,392
Loans with no related allowance recorded, average recorded investment	4,304	4,996
Loans with an allowance recorded, recorded investment	48	2,660
Loans with an allowance recorded, unpaid principal balance	48	3,135
Related allowance	48	1,267
Loans with an allowance recorded, average recorded investment	1,981	2,567
Recorded investment	7,380	6,269
Unpaid principal balance	9,120	7,527
Average recorded investment	6,285	7,563
Commercial and Industrial Portfolio Segment [Member]
Loans with no related allowance recorded, recorded investment	1,142	322
Loans with no related allowance recorded, unpaid principal balance	2,202	465
Loans with no related allowance recorded, average recorded investment	411	1,947
Loans with an allowance recorded, recorded investment	34	2,360
Loans with an allowance recorded, unpaid principal balance	34	2,835
Related allowance	34	1,207
Loans with an allowance recorded, average recorded investment	1,882	1,619
Recorded investment	1,176	2,682
Unpaid principal balance	2,236	3,300
Average recorded investment	2,293	3,566
Construction and Development Excluding Undeveloped Land Portfolio Segment [Member]
Loans with no related allowance recorded, recorded investment	664	538
Loans with no related allowance recorded, unpaid principal balance	834	708
Loans with no related allowance recorded, average recorded investment	559	108
Loans with an allowance recorded, recorded investment
Loans with an allowance recorded, unpaid principal balance
Related allowance
Loans with an allowance recorded, average recorded investment		182
Recorded investment	664	538
Unpaid principal balance	834	708
Average recorded investment	559	290
Undevelopment Land Portfolio Segment [Member]
Loans with no related allowance recorded, recorded investment	474	233
Loans with no related allowance recorded, unpaid principal balance	506	265
Loans with no related allowance recorded, average recorded investment	425	76
Loans with an allowance recorded, recorded investment		241
Loans with an allowance recorded, unpaid principal balance		241
Related allowance		1
Loans with an allowance recorded, average recorded investment	48	149
Recorded investment	474	474
Unpaid principal balance	506	506
Average recorded investment	473	225
Real Estate Mortgage Portfolio Segment [Member]
Loans with no related allowance recorded, recorded investment	5,052	2,516
Loans with no related allowance recorded, unpaid principal balance	5,530	2,954
Loans with no related allowance recorded, average recorded investment	2,909	2,847
Loans with an allowance recorded, recorded investment	14
Loans with an allowance recorded, unpaid principal balance	14
Related allowance	14
Loans with an allowance recorded, average recorded investment	5	554
Recorded investment	5,066	2,516
Unpaid principal balance	5,544	2,954
Average recorded investment	2,914	3,401
Real Estate Mortgage Portfolio Segment [Member] | Commercial Investment [Member]
Loans with no related allowance recorded, recorded investment	52	107
Loans with no related allowance recorded, unpaid principal balance	53	107
Loans with no related allowance recorded, average recorded investment	110	193
Loans with an allowance recorded, recorded investment
Loans with an allowance recorded, unpaid principal balance
Related allowance
Loans with an allowance recorded, average recorded investment
Recorded investment	52	107
Unpaid principal balance	53	107
Average recorded investment	110	193
Real Estate Mortgage Portfolio Segment [Member] | Owner Occupied Commercial [Member]
Loans with no related allowance recorded, recorded investment	3,332	1,042
Loans with no related allowance recorded, unpaid principal balance	3,789	1,479
Loans with no related allowance recorded, average recorded investment	1,678	1,356
Loans with an allowance recorded, recorded investment
Loans with an allowance recorded, unpaid principal balance
Related allowance
Loans with an allowance recorded, average recorded investment		554
Recorded investment	3,332	1,042
Unpaid principal balance	3,789	1,479
Average recorded investment	1,678	1,910
Real Estate Mortgage Portfolio Segment [Member] | One to Four Family Residential [Member]
Loans with no related allowance recorded, recorded investment	1,637	984
Loans with no related allowance recorded, unpaid principal balance	1,657	985
Loans with no related allowance recorded, average recorded investment	935	980
Loans with an allowance recorded, recorded investment	14
Loans with an allowance recorded, unpaid principal balance	14
Related allowance	14
Loans with an allowance recorded, average recorded investment	5
Recorded investment	1,651	984
Unpaid principal balance	1,671	985
Average recorded investment	940	980
Real Estate Mortgage Portfolio Segment [Member] | Home Equity First Lien [Member]
Loans with no related allowance recorded, recorded investment
Loans with no related allowance recorded, unpaid principal balance
Loans with no related allowance recorded, average recorded investment		3
Loans with an allowance recorded, recorded investment
Loans with an allowance recorded, unpaid principal balance
Related allowance
Loans with an allowance recorded, average recorded investment
Recorded investment
Unpaid principal balance
Average recorded investment		3
Real Estate Mortgage Portfolio Segment [Member] | Home Equity Junior Lien [Member]
Loans with no related allowance recorded, recorded investment	31	383
Loans with no related allowance recorded, unpaid principal balance	31	383
Loans with no related allowance recorded, average recorded investment	186	315
Loans with an allowance recorded, recorded investment
Loans with an allowance recorded, unpaid principal balance
Related allowance
Loans with an allowance recorded, average recorded investment
Recorded investment	31	383
Unpaid principal balance	31	383
Average recorded investment	186	315
Consumer Portfolio Segment [Member]
Loans with no related allowance recorded, recorded investment
Loans with no related allowance recorded, unpaid principal balance
Loans with no related allowance recorded, average recorded investment		18
Loans with an allowance recorded, recorded investment		59
Loans with an allowance recorded, unpaid principal balance		59
Related allowance		59
Loans with an allowance recorded, average recorded investment	46	63
Recorded investment		59
Unpaid principal balance		59
Average recorded investment	$ 46	$ 81