Note 6 - Stockholders' Equity - Options Outstanding and Exercisable, By Exercise Range (Details) shares in Thousands | 3 Months Ended |
Jun. 30, 2017$ / sharesshares |
Options vested, number of shares (in shares) | shares | 1,859 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.75 |
Lower range of exercise price (in dollars per share) | 1.35 |
Upper range of exercise price (in dollars per share) | $ 18.90 |
Options outstanding, number of shares (in shares) | shares | 4,574 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 135 days |
Range 1 [Member] | |
Options vested, number of shares (in shares) | shares | 29 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.35 |
Lower range of exercise price (in dollars per share) | 1.35 |
Upper range of exercise price (in dollars per share) | $ 1.35 |
Options outstanding, number of shares (in shares) | shares | 103 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 350 days |
Range 2 [Member] | |
Options vested, number of shares (in shares) | shares | 660 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.64 |
Lower range of exercise price (in dollars per share) | 1.64 |
Upper range of exercise price (in dollars per share) | $ 1.64 |
Options outstanding, number of shares (in shares) | shares | 2,000 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 237 days |
Range 3 [Member] | |
Options vested, number of shares (in shares) | shares | 108 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.78 |
Lower range of exercise price (in dollars per share) | 1.75 |
Upper range of exercise price (in dollars per share) | $ 2 |
Options outstanding, number of shares (in shares) | shares | 575 |
Options outstanding, weighted-average remaining contractual life (Year) | 9 years 43 days |
Range 4 [Member] | |
Options vested, number of shares (in shares) | shares | 166 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.48 |
Lower range of exercise price (in dollars per share) | 2.59 |
Upper range of exercise price (in dollars per share) | $ 3.99 |
Options outstanding, number of shares (in shares) | shares | 460 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 295 days |
Range 5 [Member] | |
Options vested, number of shares (in shares) | shares | 304 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 4.32 |
Lower range of exercise price (in dollars per share) | 4.32 |
Upper range of exercise price (in dollars per share) | $ 4.32 |
Options outstanding, number of shares (in shares) | shares | 634 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 29 days |
Range 6 [Member] | |
Options vested, number of shares (in shares) | shares | 531 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 6.28 |
Lower range of exercise price (in dollars per share) | 5.18 |
Upper range of exercise price (in dollars per share) | $ 6.61 |
Options outstanding, number of shares (in shares) | shares | 741 |
Options outstanding, weighted-average remaining contractual life (Year) | 7 years 40 days |
Range 7 [Member] | |
Options vested, number of shares (in shares) | shares | 50 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 6.83 |
Lower range of exercise price (in dollars per share) | 6.83 |
Upper range of exercise price (in dollars per share) | $ 6.83 |
Options outstanding, number of shares (in shares) | shares | 50 |
Options outstanding, weighted-average remaining contractual life (Year) | 6 years 233 days |
Range 8 [Member] | |
Options vested, number of shares (in shares) | shares | 5 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 7.20 |
Lower range of exercise price (in dollars per share) | 7.20 |
Upper range of exercise price (in dollars per share) | $ 7.20 |
Options outstanding, number of shares (in shares) | shares | 5 |
Options outstanding, weighted-average remaining contractual life (Year) | 1 year 240 days |
Range 9 [Member] | |
Options vested, number of shares (in shares) | shares | 5 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 11.40 |
Lower range of exercise price (in dollars per share) | 11.40 |
Upper range of exercise price (in dollars per share) | $ 11.40 |
Options outstanding, number of shares (in shares) | shares | 5 |
Options outstanding, weighted-average remaining contractual life (Year) | 1 year 54 days |
Range 10 [Member] | |
Options vested, number of shares (in shares) | shares | 1 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 18.90 |
Lower range of exercise price (in dollars per share) | 18.90 |
Upper range of exercise price (in dollars per share) | $ 18.90 |
Options outstanding, number of shares (in shares) | shares | 1 |
Options outstanding, weighted-average remaining contractual life (Year) | 14 days |