Note 6 - Marketable Securities - Short-term and Long-term Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
US States and Political Subdivisions Debt Securities [Member]
Amortized Cost	$ 32,661	$ 30,004
Unrealized Gains	20	32
Unrealized Losses	(49)	(18)
Fair Value	32,632	30,018
Corporate Debt Securities [Member]
Amortized Cost	25,932	29,316
Unrealized Gains	5	7
Unrealized Losses	(31)	(79)
Fair Value	25,906	29,244
US Government Agencies Debt Securities [Member]
Amortized Cost	19,857	$ 20,048
Unrealized Gains	9
Unrealized Losses	(23)	$ (71)
Fair Value	19,843	19,977
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Amortized Cost	$ 1,566
Unrealized Gains
Unrealized Losses	$ (1)
Fair Value	1,565
Bank Time Deposits [Member]
Amortized Cost	5,656	5,656
Unrealized Gains	$ 12	5
Unrealized Losses		(15)
Fair Value	$ 5,668	5,646
Amortized Cost	85,672	85,024
Unrealized Gains	46	44
Unrealized Losses	(104)	(183)
Fair Value	$ 85,614	$ 84,885