Note 7 - Securities Available for Sale - Summary of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Securities available for sale, amortized cost	$ 83,081	$ 78,801
Investment securities available for sale, gross unrealized gains	0	104
Investment securities available for sale, gross unrealized losses	(1,907)	(1,433)
Securities available for sale	81,174	77,472
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Securities available for sale, amortized cost	4,831	91
Investment securities available for sale, gross unrealized gains	0	2
Investment securities available for sale, gross unrealized losses	(35)	0
Securities available for sale	4,796	93
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Securities available for sale, amortized cost	217	223
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(9)	(5)
Securities available for sale	208	218
Collateralized Mortgage Obligations [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Securities available for sale, amortized cost	4,605	4,834
Investment securities available for sale, gross unrealized gains	0	1
Investment securities available for sale, gross unrealized losses	(154)	(78)
Securities available for sale	4,451	4,757
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, amortized cost	9,653	5,148
Investment securities available for sale, gross unrealized gains	0	3
Investment securities available for sale, gross unrealized losses	(198)	(83)
Securities available for sale	9,455	5,068
Other Marketable Securities [Member]
Securities available for sale, amortized cost	73,428	73,653
Investment securities available for sale, gross unrealized gains	0	101
Investment securities available for sale, gross unrealized losses	(1,709)	(1,350)
Securities available for sale	71,719	72,404
Other Marketable Securities [Member] | US Government Agencies Debt Securities [Member]
Securities available for sale, amortized cost	69,964	69,962
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(1,552)	(1,201)
Securities available for sale	68,412	68,761
Other Marketable Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Securities available for sale, amortized cost	2,386	2,699
Investment securities available for sale, gross unrealized gains	0	2
Investment securities available for sale, gross unrealized losses	(15)	(8)
Securities available for sale	2,371	2,693
Other Marketable Securities [Member] | Corporate Debt Securities [Member]
Securities available for sale, amortized cost	204	234
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(2)	(1)
Securities available for sale	202	233
Other Marketable Securities [Member] | Preferred Stock [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	(140)	(140)
Securities available for sale	560	560
Other Marketable Securities [Member] | Equity Securities [Member]
Securities available for sale, amortized cost	174	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	$ 174	$ 157