Note 4 - Securities - Summary of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt securities, amortized cost	$ 100,752	$ 100,446
Debt securities, gross unrealized gains	40	159
Debt securities, gross unrealized losses	(3,283)	(1,255)
Debt securities, fair value	97,509	99,350
US Treasury and Government [Member]
Debt securities, amortized cost	4,534	4,541
Debt securities, gross unrealized gains
Debt securities, gross unrealized losses	(139)	(69)
Debt securities, fair value	4,395	4,472
US Government-sponsored Enterprises Debt Securities [Member]
Debt securities, amortized cost	17,058	14,136
Debt securities, gross unrealized gains		2
Debt securities, gross unrealized losses	(508)	(212)
Debt securities, fair value	16,550	13,926
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt securities, amortized cost	28,526	20,904
Debt securities, gross unrealized gains		7
Debt securities, gross unrealized losses	(862)	(153)
Debt securities, fair value	27,664	20,758
Collateralized Mortgage Obligations [Member]
Debt securities, amortized cost	20,171	22,607
Debt securities, gross unrealized gains	36	25
Debt securities, gross unrealized losses	(1,002)	(708)
Debt securities, fair value	19,205	21,924
US States and Political Subdivisions Debt Securities [Member]
Debt securities, amortized cost	22,943	29,249
Debt securities, gross unrealized gains	3	87
Debt securities, gross unrealized losses	(686)	(96)
Debt securities, fair value	22,260	29,240
Corporate Debt Securities [Member]
Debt securities, amortized cost	7,520	9,009
Debt securities, gross unrealized gains	1	38
Debt securities, gross unrealized losses	(86)	(17)
Debt securities, fair value	$ 7,435	$ 9,030