Note 10 - Stock-based Compensation - Summary of Option Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands |
12 Months Ended |
|
|
|
|
Mar. 31, 2017 |
Mar. 31, 2016 |
Mar. 31, 2015 |
Mar. 31, 2014 |
Mar. 31, 2017 |
Mar. 31, 2016 |
Mar. 31, 2015 |
Mar. 31, 2014 |
| Outstanding, Numbers of Shares (in shares) |
515,720
|
437,248
|
398,172
|
|
|
|
|
|
| Outstanding, Weighted average exercise price (in dollars per share) |
$ 64.32
|
$ 55.81
|
$ 38.75
|
|
|
|
|
|
| Outstanding, Weighted average exercise price (in dollars per share) |
$ 64.32
|
$ 55.81
|
$ 38.75
|
$ 38.75
|
$ 75.78
|
$ 64.32
|
$ 55.81
|
$ 38.75
|
| Outstanding, Weighted average remaining contractual term (Year) |
5 years
|
5 years 73 days
|
4 years 328 days
|
4 years 146 days
|
|
|
|
|
| Outstanding, Aggregate intrinsic value |
|
|
|
|
$ 23,956
|
$ 16,561
|
$ 9,445
|
$ 20,505
|
| Granted, Numbers of Shares (in shares) |
134,955
|
184,030
|
147,720
|
|
|
|
|
|
| Granted, Weighted average exercise price (in dollars per share) |
$ 102.52
|
$ 72.89
|
$ 88.62
|
|
|
|
|
|
| Granted, Weighted average remaining contractual term (Year) |
5 years 182 days
|
6 years 255 days
|
7 years
|
|
|
|
|
|
| Forfeited, Numbers of Shares (in shares) |
(35,015)
|
(16,334)
|
(26,466)
|
|
|
|
|
|
| Forfeited, Weighted average exercise price (in dollars per share) |
$ 87.50
|
$ 75.16
|
$ 64.62
|
|
|
|
|
|
| Outstanding, Aggregate intrinsic value |
|
|
|
|
23,956
|
16,561
|
9,445
|
$ 20,505
|
| Forfeited, Weighted average remaining contractual term (Year) |
4 years 182 days
|
6 years 182 days
|
|
|
|
|
|
|
| Expired, Numbers of Shares (in shares) |
(904)
|
|
|
|
|
|
|
|
| Expired, Weighted average exercise price (in dollars per share) |
$ 41.51
|
|
|
|
|
|
|
|
| Exercised, Numbers of Shares (in shares) |
(104,395)
|
(89,224)
|
(82,178)
|
|
|
|
|
|
| Exercised, Weighted average exercise price (in dollars per share) |
$ 50.12
|
$ 38.28
|
$ 28.87
|
|
|
|
|
|
| Outstanding, Numbers of Shares (in shares) |
510,361
|
515,720
|
437,248
|
398,172
|
|
|
|
|
| Outstanding, Weighted average exercise price (in dollars per share) |
$ 75.78
|
$ 64.32
|
$ 55.81
|
$ 38.75
|
|
|
|
|
| Exercisable, Weighted average remaining contractual term (Year) |
3 years 328 days
|
3 years 219 days
|
3 years 219 days
|
|
|
|
|
|
| Exercisable, Aggregate intrinsic value |
|
|
|
|
$ 9,847
|
$ 8,481
|
$ 6,341
|
|
| Exercisable, Numbers of Shares (in shares) |
|
|
|
|
136,595
|
157,457
|
163,210
|
|
| Exercisable, Weighted average exercise price (in dollars per share) |
|
|
|
|
$ 50.61
|
$ 42.49
|
$ 33.35
|
|