Note 2 - Investments - Current Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available for sale securities, amortized cost	$ 29,166
Available for sale securities, unrealized loss	(49)
Available for sale securities, fair market value	29,117
Corporate Bond Securities [Member]
Available for sale securities, amortized cost	22,100
Available for sale securities, unrealized loss	(46)
Available for sale securities, fair market value	22,054
Municipal Bonds [Member]
Available for sale securities, amortized cost	3,727
Available for sale securities, unrealized loss	(1)
Available for sale securities, fair market value	3,726
US Government Agencies Debt Securities [Member]
Available for sale securities, amortized cost	3,339
Available for sale securities, unrealized loss	(2)
Available for sale securities, fair market value	$ 3,337