v3.5.0.1

Fair Value of Financial Assets and Liabilities - Summary of Short-Term Investments (Details) - USD ($) | 12 Months Ended
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Apr. 30, 2016 | Apr. 30, 2015
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | $ 50,692,000 | $ 52,758,000
Gross Unrealized Gains | 5,000 | 30,000
Gross Unrealized Losses | (15,000) | (58,000)
Fair Value | 50,682,000 | 52,730,000
Impairment Charges | 0 | 0
Certificates of deposit |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | 7,090,000 | 4,000,000
Gross Unrealized Gains | 0 | 4,000
Gross Unrealized Losses | (1,000) | 0
Fair Value | 7,089,000 | 4,004,000
Municipal debt securities |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost |  | 4,564,000
Gross Unrealized Gains |  | 17,000
Gross Unrealized Losses |  | (16,000)
Fair Value |  | 4,565,000
Commercial paper |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | 4,043,000 | 6,269,000
Gross Unrealized Gains | 0 | 4,000
Gross Unrealized Losses | 0 | 0
Fair Value | 4,043,000 | 6,273,000
U.S. Treasury securities |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | 8,764,000 | 11,814,000
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | (11,000)
Fair Value | 8,764,000 | 11,803,000
US government agencies debt securities |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | 24,841,000 | 17,007,000
Gross Unrealized Gains | 4,000 | 1,000
Gross Unrealized Losses | (9,000) | (3,000)
Fair Value | 24,836,000 | 17,005,000
Corporate debt securities |  |
Schedule of Available-for-Sale Securities [Line Items] |  |
Cost | 5,954,000 | 9,104,000
Gross Unrealized Gains | 1,000 | 4,000
Gross Unrealized Losses | (5,000) | (28,000)
Fair Value | $ 5,950,000 | $ 9,080,000

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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 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 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562 + Details
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 + Details
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- Definition The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 + Details
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