Note 12 - Stockholders' Equity - Weighted Average Fair Value Assumptions (Details)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Volatility		45.91%	37.47%	46.02%
Risk-free interest rate		2.55%	2.23%	2.29%
Dividend yield		0.00%	0.00%	0.00%
Pre-vest cancellation rate	[1]	2.68%	4.06%	1.87%
Post-vest cancellation rate	[2]	3.34%	3.45%	3.44%
Suboptimal exercise factor	[3]	1.49%	1.31%	1.69%
Expected life (Year)		5 years 335 days	4 years 80 days	5 years 182 days

[1] The pre-vest cancellation rate was calculated on an annual basis and is presented here on an annual basis.

[2] The post-vest cancellation rate was calculated on a monthly basis and is presented here on an annual basis.

[3] The ratio of the stock price to strike price at the time of exercise of the option.