Note 4 - Investments (Details Textual)	1 Months Ended	12 Months Ended
	Jul. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Total		99
Equity Securities, FV-NI		$ 1,387,000
Equity Securities, FV-NI, Accumulated Gross Unrealized Loss		607,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount		3,066,000
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount		7,000,000
Other Income [Member]
Cost-method Investments, Realized Gains				$ 1,138,000
Minority Interest in Early Stage Private Company [Member]
Cost Method Investments, Amount Sold	$ 8,759,000
Amount Held in Escrow Related to Cost Method Investments Sold	$ 2,414,000
Other Noncurrent Assets [Member]
Equity Securities without Readily Determinable Fair Value, Amount		16,866,000
Other Noncurrent Assets [Member] | Equity Securities, Fair Value Based on Observable Transaction [Member]
Equity Securities without Readily Determinable Fair Value, Amount		6,066,000
Accounting Standards Update 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 0			$ 0