Note 6 - Stockholders' Equity - Options Outstanding and Exercisable, by Exercise Range (Details) shares in Thousands | 9 Months Ended |
Dec. 31, 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 | 4,286 |
Options outstanding, weighted-average remaining contractual life (Year) | 7 years 332 days |
Options vested, number of shares (in shares) | shares | 2,110 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.39 |
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 | 92 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 142 days |
Options vested, number of shares (in shares) | shares | 38 |
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 | 1,925 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 54 days |
Options vested, number of shares (in shares) | shares | 873 |
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 | 560 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 273 days |
Options vested, number of shares (in shares) | shares | 192 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 1.86 |
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 | 448 |
Options outstanding, weighted-average remaining contractual life (Year) | 8 years 94 days |
Options vested, number of shares (in shares) | shares | 206 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 3.44 |
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 | 627 |
Options outstanding, weighted-average remaining contractual life (Year) | 7 years 211 days |
Options vested, number of shares (in shares) | shares | 378 |
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 266 days |
Options vested, number of shares (in shares) | shares | 287 |
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 | 205 |
Options outstanding, weighted-average remaining contractual life (Year) | 6 years 73 days |
Options vested, number of shares (in shares) | shares | 176 |
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 51 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 58 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) | 233 days |
Options vested, number of shares (in shares) | shares | 5 |
Options vested, weighted-average exercise price per share (in dollars per share) | $ 11.40 |