Note 2 - Investments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Debt Securities, Current	$ 29,100	$ 0
Payments to Acquire Investments	48,943	947	$ 580
Proceeds from Sale and Maturity of Marketable Securities	18,649
Available-for-sale Securities, Equity Securities, Noncurrent	5,000	1,500
Available-for-sale Equity Securities, Amortized Cost Basis	4,100	4,000
Available-for-sale Equity Securities, Acquired During Period, Cost Basis	900	900
Other than Temporary Impairment Losses, Investments	$ 1,000	$ 2,500