Note 9 - Allowance for Loan Losses and Credit Quality Information - Purchased Loans Acquired Through Acquisition (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Purchased performing loans:
Carrying Amount	$ 400,000
Purchased Performing Loans [Member]
Purchased performing loans:
Contractual Principle Receivable	9,447,000	$ 10,128,000
Accretable Difference	(218,000)	(231,000)
Carrying Amount	9,229,000	9,897,000
Contractual Principle Receivable, change due to payments/refinances	(681,000)
Accretable Difference, change due to payments/refinances	13,000
Carrying Amount, change due to payments/refinances	(668,000)
Purchased Credit Impaired Loans [Member]
Purchased performing loans:
Contractual Principle Receivable	400,000	402,000
Carrying Amount	363,000	363,000
Contractual Principle Receivable, change due to payments/refinances	(2,000)
Carrying Amount, change due to payments/refinances	0
Non-accretable difference	(37,000)	$ (39,000)
Non-accretable difference, change due to payments/refinances	$ 2,000