Note 14 - Available-for-sale Securities - Available-for-sale Securities (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale securities, amortized cost	$ 1,496,000
Available-for-sale securities, gross unrealized losses	(3,000)
Available-for-sale securities, fair value	1,493,000
Debt Security, Corporate, US [Member]
Available-for-sale securities, amortized cost	396,000
Available-for-sale securities, gross unrealized losses	(2,000)
Available-for-sale securities, fair value	394,000
Certificates of Deposit [Member]
Available-for-sale securities, amortized cost	600,000
Available-for-sale securities, gross unrealized losses	0
Available-for-sale securities, fair value	600,000
Certificates of Deposit, Maturing Within One to Five Years [Member]
Available-for-sale securities, amortized cost	500,000
Available-for-sale securities, gross unrealized losses	(1,000)
Available-for-sale securities, fair value	$ 499,000

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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