Note 4 - Stockholders' Equity (Detail) - Stock Options, Valuation Assumptions (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Stock Options [Member]
Expected life (in years)	4 years 284 days	4 years 211 days
Volatility	56.40%	60.60%
Risk-free interest rate	0.80%	0.78%
Expected dividend	0.00%	0.00%
Weighted average fair value per share of options granted during the period (in Dollars per share)	$ 7.54	$ 3.23
Employee Stock Purchase Plan [Member]
Expected life (in years)	1 year 3 months	1 year 3 months
Volatility	46.10%	47.30%
Risk-free interest rate	0.19%	0.35%
Expected dividend	0.00%	0.00%
Weighted average fair value per share of employee stock purchase plan rights granted during the period (in Dollars per share)	$ 5.28	$ 2.03

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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