Note 10 - Share Option and Equity Incentive Plan - Valuation Assumptions, Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expected dividend yield (%)	0.00%
Weighted-average exercise price ($) (in dollars per share)	$ 10.29
Employee Stock Option [Member]
Expected dividend yield (%)
Expected volatility (%)	43.70%	44.11%	46.87%
Risk-free interest rate (%)	1.53%	1.66%	1.86%
Expected life of option (years) (Year)	6 years 58 days	6 years 69 days	6 years 69 days
Weighted-average share price ($) (in dollars per share)	$ 10.29	$ 14.15	$ 19.66
Weighted-average exercise price ($) (in dollars per share)	$ 10.29	$ 14.15	$ 19.66
Model used	Black-Scholes Model	Black-Scholes Model	Black-Scholes Model