Note 2 - Stock-Based Compensation (Details) - Employee Stock Purchase Plan Fair Value Assumptions	3 Months Ended		6 Months Ended		3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013 Two Thousand Four Employee Stock Purchase Plan [Member]	Mar. 31, 2012 Two Thousand Four Employee Stock Purchase Plan [Member]
Note 2 - Stock-Based Compensation (Details) - Employee Stock Purchase Plan Fair Value Assumptions [Line Items]
Expected term (years)	4 years 36 days	3 years 292 days	4 years	4 years 36 days	6 months	6 months
Expected volatility	50.00%	53.40%	51.00%	53.40%	28.50%	50.70%
Risk-free interest rate	0.70%	0.60%	0.70%	0.60%	0.10%	0.10%
Dividend yield	0.00%	0.00%	0.00%		0.00%	0.00%