|
Summary of Short-Term Investments (Detail) (USD $)
In Thousands, unless otherwise specified |
Oct. 31, 2014
|
Apr. 30, 2014
|
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | $ 48,615 | $ 40,692 |
| Gross Unrealized Gains | 38 | 19 |
| Gross Unrealized Losses | (14) | (11) |
| Fair Value | 48,639 | 40,700 |
|
Certificates of Deposit
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 7,510 | 7,466 |
| Gross Unrealized Gains | 4 | 17 |
| Gross Unrealized Losses | (2) | (9) |
| Fair Value | 7,512 | 7,474 |
|
Municipal Bonds
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 3,278 | |
| Gross Unrealized Gains | 19 | |
| Gross Unrealized Losses | (10) | |
| Fair Value | 3,287 | |
|
Commercial Paper
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 5,997 | |
| Gross Unrealized Gains | 2 | |
| Fair Value | 5,999 | |
|
US Treasury notes
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 31,830 | 33,226 |
| Gross Unrealized Gains | 13 | 2 |
| Gross Unrealized Losses | (2) | (2) |
| Fair Value | $ 31,841 | $ 33,226 |