Note 1 - Summary of Significant Accounting Policies (Details Textual) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018 USD ($)	Dec. 31, 2017
Period Look-back, Quarters	32	28
Allowance for Loan and Lease Losses, Period Increase (Decrease), Total	$ 1.3

Amount of increase (decrease) of allowance reserve for credit loss.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration