Note 4 - Fair Value Measurement (Details) - Discounted Cash Flow Assumptions - Auction Rate Securities [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-liquidity (months)	24 months	24 months
Expected return	2.90%	2.90%
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.30%	4.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	7.30%	7.00%