Note 6 - Stockholders' Equity - Options Outstanding and Exercisable, By Exercise Range (Details) shares in Thousands | 6 Months Ended |
Sep. 30, 2017$ / sharesshares |
Lower range of exercise price (in dollars per share) | $ 1.35 |
Upper range of exercise price (in dollars per share) | $ 11.40 |
Options outstanding, number of shares (in shares) | shares | 4,450 |
Options outstanding, weighted-average remaining contractual life (Year) | 7 years 310 days |
Options vested, number of shares (in shares) | shares | 2,111 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.63 |
Range 1 [Member] | |
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 259 days |
Options vested, number of shares (in shares) | shares | 36 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.35 |
Range 2 [Member] | |
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 | 1,953 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 102 days |
Options vested, number of shares (in shares) | shares | 782 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.64 |
Range 3 [Member] | |
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 | 543 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 222 days |
Options vested, number of shares (in shares) | shares | 137 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.78 |
Range 4 [Member] | |
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 204 days |
Options vested, number of shares (in shares) | shares | 195 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.45 |
Range 5 [Member] | |
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) | 7 years 302 days |
Options vested, number of shares (in shares) | shares | 343 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 4.32 |
Range 6 [Member] | |
Lower range of exercise price (in dollars per share) | 5.18 |
Upper range of exercise price (in dollars per share) | $ 6.30 |
Options outstanding, number of shares (in shares) | shares | 369 |
Options outstanding, weighted-average remaining contractual life (Year) | 6 years 357 days |
Options vested, number of shares (in shares) | shares | 273 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 5.95 |
Range 7 [Member] | |
Lower range of exercise price (in dollars per share) | 6.83 |
Upper range of exercise price (in dollars per share) | $ 6.61 |
Options outstanding, number of shares (in shares) | shares | 328 |
Options outstanding, weighted-average remaining contractual life (Year) | 4 years 91 days |
Options vested, number of shares (in shares) | shares | 285 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 6.61 |
Range 8 [Member] | |
Lower range of exercise price (in dollars per share) | 7.20 |
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 142 days |
Options vested, number of shares (in shares) | shares | 50 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 6.83 |
Range 9 [Member] | |
Lower range of exercise price (in dollars per share) | 11.40 |
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 149 days |
Options vested, number of shares (in shares) | shares | 5 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 7.20 |
Range 10 [Member] | |
Lower range of exercise price (in dollars per share) | 18.90 |
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) | 324 days |
Options vested, number of shares (in shares) | shares | 5 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 11.40 |