Note 1 - Fair Value of Financial Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair value	$ 36,061	$ 39,128
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair value	8,140	9,442
Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Fair value	27,921	29,686
Fair Value, Inputs, Level 1 [Member]
Fair value	36,061	39,128
Money Market Funds [Member]
Fair value	8,140	9,442
Commercial Paper [Member]
Fair value	$ 27,921	$ 29,686