|
Summary of Short-Term Investments (Detail) (USD $)
In Thousands, unless otherwise specified |
Apr. 30, 2014
|
Apr. 30, 2013
|
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | $ 40,692 | $ 70,370 |
| Gross Unrealized Gains | 19 | 24 |
| Gross Unrealized Losses | (11) | (104) |
| Fair Value | 40,700 | 70,290 |
|
Certificates of Deposit
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 7,466 | 9,230 |
| Gross Unrealized Gains | 17 | 9 |
| Gross Unrealized Losses | (9) | (4) |
| Fair Value | 7,474 | 9,235 |
|
U.S. Treasury securities
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 33,226 | 61,140 |
| Gross Unrealized Gains | 2 | 15 |
| Gross Unrealized Losses | (2) | (100) |
| Fair Value | $ 33,226 | $ 61,055 |