|
Summary of Short-Term Investments (Detail) (USD $)
In Thousands, unless otherwise specified |
Jul. 31, 2014
|
Apr. 30, 2014
|
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | $ 67,862 | $ 40,692 |
| Gross Unrealized Gains | 46 | 19 |
| Gross Unrealized Losses | (10) | (11) |
| Fair Value | 67,898 | 40,700 |
|
Certificates of Deposit
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 7,230 | 7,466 |
| Gross Unrealized Gains | 1 | 17 |
| Gross Unrealized Losses | (7) | (9) |
| Fair Value | 7,224 | 7,474 |
|
Municipal Bonds
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 3,377 | |
| Gross Unrealized Gains | 31 | |
| Gross Unrealized Losses | (1) | |
| Fair Value | 3,407 | |
|
Commercial Paper
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 5,997 | |
| Gross Unrealized Losses | (1) | |
| Fair Value | 5,996 | |
|
US Treasury securities
|
||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost | 51,258 | 33,226 |
| Gross Unrealized Gains | 14 | 2 |
| Gross Unrealized Losses | (1) | (2) |
| Fair Value | $ 51,271 | $ 33,226 |