Note 4 - Investments (Details Textual)			1 Months Ended		3 Months Ended			12 Months Ended
	Dec. 30, 2016 USD ($)	Dec. 23, 2015	Jan. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Equity Method Investment, Other than Temporary Impairment									$ 792,000
Number of Investee Companies		1
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments								$ 37,000	2,034,000
Cost Method Investments				$ 1,015,000			$ 1,015,000	1,272,000	1,015,000
Cost-method Investments, Other than Temporary Impairment								750,000
Investments, Unfunded Commitments								$ 1,000,000
Lumense Inc. [Member]
Cost Method Investments					$ 0	$ 50,000
Cost-method Investments, Other than Temporary Impairment					$ 50,000	$ 700,000
Privately-held Technology Company [Member]
Investments, Unfunded Commitments	$ 1,000,000
Investment, Unfunded Commitments, to Be Held in Escrow	$ 500,000
NKD Enterprises LLC [Member]
Equity Method Investment, Ownership Percentage				25.50%			25.50%	25.50%	25.50%
Equity Method Investment, Other than Temporary Impairment				$ 792,000
Lancope, Inc. [Member]
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments							$ 2,034,000
Cost Method Investments				214,000			214,000		$ 214,000
Proceeds from Sale of Other Investments			$ 2,248,000
Held Escrow Period									1 year 180 days
Estimated Portion of Escrow				$ 390,000			$ 390,000		$ 390,000