v2.4.0.6

Fair Value of Financial Assets and Liabilities (Details 2) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2012	Apr. 30, 2012
Cash equivalents:
Restricted cash	$ 604	$ 500
Short-term investments:
Short-term investments	74,660	50,834
Quoted prices in active markets for identical assets (Level 1) [Member]
Cash equivalents:
Restricted cash	604	500
Significant other observable inputs (Level 2) [Member]
Cash equivalents:
Restricted cash
Significant unobservable inputs (Level 3) [Member]
Cash equivalents:
Restricted cash
Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	5,447	29,006
Short-term investments:
Short-term investments	74,660	50,834
Total assets	80,711	80,340
Fair Value, Measurements, Recurring [Member] | Certificates of deposit (U.S. Gov. guaranteed) [Member]
Short-term investments:
Short-term investments	7,344	4,496
Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Cash equivalents:
Cash equivalents	447	288
Fair Value, Measurements, Recurring [Member] | U.S. Treasury bills [Member]
Cash equivalents:
Cash equivalents	5,000	7,499
Fair Value, Measurements, Recurring [Member] | Corporate bonds (U.S. Gov. guaranteed) [Member]
Cash equivalents:
Cash equivalents		21,219
Short-term investments:
Short-term investments	18,167	18,239
Fair Value, Measurements, Recurring [Member] | U.S. Treasury notes [Member]
Short-term investments:
Short-term investments	49,149	28,099
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Cash equivalents:
Cash equivalents	5,447	29,006
Short-term investments:
Short-term investments	74,660	50,834
Total assets	80,711	80,340
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member] | Certificates of deposit (U.S. Gov. guaranteed) [Member]
Short-term investments:
Short-term investments	7,344	4,496
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member] | Money market funds [Member]
Cash equivalents:
Cash equivalents	447	288
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member] | U.S. Treasury bills [Member]
Cash equivalents:
Cash equivalents	5,000	7,499
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member] | Corporate bonds (U.S. Gov. guaranteed) [Member]
Cash equivalents:
Cash equivalents		21,219
Short-term investments:
Short-term investments	18,167	18,239
Fair Value, Measurements, Recurring [Member] | Quoted prices in active markets for identical assets (Level 1) [Member] | U.S. Treasury notes [Member]
Short-term investments:
Short-term investments	49,149	28,099
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member]
Cash equivalents:
Cash equivalents
Short-term investments:
Short-term investments
Total assets
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member] | Certificates of deposit (U.S. Gov. guaranteed) [Member]
Short-term investments:
Short-term investments
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member] | Money market funds [Member]
Cash equivalents:
Cash equivalents
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member] | U.S. Treasury bills [Member]
Cash equivalents:
Cash equivalents
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member] | Corporate bonds (U.S. Gov. guaranteed) [Member]
Cash equivalents:
Cash equivalents
Short-term investments:
Short-term investments
Fair Value, Measurements, Recurring [Member] | Significant other observable inputs (Level 2) [Member] | U.S. Treasury notes [Member]
Short-term investments:
Short-term investments
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member]
Cash equivalents:
Cash equivalents
Short-term investments:
Short-term investments
Total assets
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member] | Certificates of deposit (U.S. Gov. guaranteed) [Member]
Short-term investments:
Short-term investments
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member] | Money market funds [Member]
Cash equivalents:
Cash equivalents
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member] | U.S. Treasury bills [Member]
Cash equivalents:
Cash equivalents
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member] | Corporate bonds (U.S. Gov. guaranteed) [Member]
Cash equivalents:
Cash equivalents
Short-term investments:
Short-term investments
Fair Value, Measurements, Recurring [Member] | Significant unobservable inputs (Level 3) [Member] | U.S. Treasury notes [Member]
Short-term investments:
Short-term investments

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- Definition

Cash equivalents fair value disclosure.

+ References

No definition available.

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Paragraph 80

-Subparagraph Exhibit 4-8, 3

-IssueDate 2006-05-01

-Chapter 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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- Definition

Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph g

-Article 7

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