Note 3 - Investment Write-down (Details Textual) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cost-method Investments, Other than Temporary Impairment				$ 255,000	$ 93,000
Lumense Inc. [Member]
Cost-method Investments, Other than Temporary Impairment	$ 250,000	$ 10,000	$ 90,000

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

No definition available.

Name:	us-gaap_CostmethodInvestmentsOtherThanTemporaryImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration