|
Summary of Short-Term Investments (Detail) (USD $)
In Thousands, unless otherwise specified |
Jan. 31, 2014
|
Apr. 30, 2013
|
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | $ 28,184 | $ 70,370 |
| Gross Unrealized Gains | 14 | 24 |
| Gross Unrealized Losses | (3) | (104) |
| Fair Value | 28,195 | 70,290 |
|
Certificates of Deposit
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 5,450 | 9,230 |
| Gross Unrealized Gains | 4 | 9 |
| Gross Unrealized Losses | (1) | (4) |
| Fair Value | 5,453 | 9,235 |
|
U.S. Treasury securities
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 22,734 | 61,140 |
| Gross Unrealized Gains | 10 | 15 |
| Gross Unrealized Losses | (2) | (100) |
| Fair Value | $ 22,742 | $ 61,055 |