Note 4 - Investments (Details Textual)		1 Months Ended	3 Months Ended			12 Months Ended
	Dec. 30, 2016 USD ($)	Jan. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments, Total							$ 1,466,000
Cost Method Investments			$ 1,035,000			$ 760,000	1,035,000
Cost-method Investments, Other than Temporary Impairment						363,000	103,000
Gain (Loss) on Sale of Investments, Total							$ 1,838,000
Privately-held Technology Company [Member]
Cost Method Investments				$ 98,000
Investments, Unfunded Commitments	$ 1,000,000
Investment, Unfunded Commitments, to Be Held in Escrow	$ 500,000
Cost Method Investments, Percent Sold				91.00%
Gain (Loss) on Sale of Investments, Total				$ 1,466,000
Lumense Inc. [Member]
Cost-method Investments, Other than Temporary Impairment					$ 250,000	$ 250,000
Final Inc. [Member]
Cost-method Investments, Other than Temporary Impairment			$ 10,000		$ 90,000
NKD Enterprises LLC [Member]
Equity Method Investment, Ownership Percentage			25.50%			25.50%	25.50%
Equity Method Investments			$ 25,000			$ 0	$ 25,000
Lancope, Inc. [Member]
Number of Investee Companies								1
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments, Total								$ 2,034,000
Cost Method Investments								$ 214,000
Proceeds from Sale of Other Investments		$ 2,248,000
Held Escrow Period								1 year 180 days
Proceeds From Issuance of Restricted Cash				$ 372,000