Note 7 - Securities Available for Sale - Summary of Securities Available for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities available for sale, amortized cost	$ 81,960	$ 78,801
Investment securities available for sale, gross unrealized gains	1	104
Investment securities available for sale, gross unrealized losses	(2,357)	(1,433)
Securities available for sale	79,604	77,472
Securities available for sale	79,604	77,472
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, amortized cost	8,593	5,148
Investment securities available for sale, gross unrealized gains	0	3
Investment securities available for sale, gross unrealized losses	(386)	(83)
Securities available for sale	8,207	5,068
Securities available for sale	8,207	5,068
Other Marketable Securities [Member]
Securities available for sale, amortized cost	73,367	73,653
Investment securities available for sale, gross unrealized gains	1	101
Investment securities available for sale, gross unrealized losses	(1,971)	(1,350)
Securities available for sale	71,397	72,404
Securities available for sale	71,397	72,404
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | Collateralized Mortgage Obligations [Member]
Securities available for sale, amortized cost	4,096	4,834
Investment securities available for sale, gross unrealized gains	0	1
Investment securities available for sale, gross unrealized losses	(250)	(78)
Securities available for sale	3,846	4,757
Securities available for sale	3,846	4,757
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale, amortized cost	203	223
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(13)	(5)
Securities available for sale	190	218
Securities available for sale	190	218
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available for sale, amortized cost	4,294	91
Investment securities available for sale, gross unrealized gains	0	2
Investment securities available for sale, gross unrealized losses	(123)	0
Securities available for sale	4,171	93
Securities available for sale	4,171	93
US Government Agencies Debt Securities [Member] | Other Marketable Securities [Member]
Securities available for sale, amortized cost	69,969	69,962
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(1,844)	(1,201)
Securities available for sale	68,125	68,761
Securities available for sale	68,125	68,761
US States and Political Subdivisions Debt Securities [Member] | Other Marketable Securities [Member]
Securities available for sale, amortized cost	2,381	2,699
Investment securities available for sale, gross unrealized gains	1	2
Investment securities available for sale, gross unrealized losses	(21)	(8)
Securities available for sale	2,361	2,693
Securities available for sale	2,361	2,693
Corporate Debt Securities [Member] | Other Marketable Securities [Member]
Securities available for sale, amortized cost	173	234
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(1)	(1)
Securities available for sale	172	233
Securities available for sale	172	233
Preferred Stock [Member] | Other Marketable Securities [Member]
Securities available for sale, amortized cost	700	700
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(105)	(140)
Securities available for sale	595	560
Securities available for sale	595	560
Equity Securities [Member] | Other Marketable Securities [Member]
Securities available for sale, amortized cost	144	58
Investment securities available for sale, gross unrealized gains	0	99
Investment securities available for sale, gross unrealized losses	0	0
Securities available for sale	144	157
Securities available for sale	$ 144	$ 157