Note 3 - Securities - Held-to-maturity Securities by Maturity (Details)	Mar. 31, 2018 USD ($)
Government sponsored mortgage-backed securities not due on a single maturity date, amortized cost	$ 15,097
Government sponsored mortgage-backed securities not due on a single maturity date, approximate fair value	$ 15,268

Amortized cost of investment in debt security measured at amortized cost (held-to-maturity), without single maturity date and not allocated over maturity grouping.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant