Note 5 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Due in one year or less, amortized cost	$ 31,372
Due in one year or less, estimated fair value	31,367
Due after one year through three years, amortized cost	623
Due after one year through three years, estimated fair value	623
	31,995
	$ 31,990