v3.7.0.1

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands | 12 Months Ended
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Apr. 30, 2017 | Apr. 30, 2016 | Apr. 30, 2015
Schedule of Income Taxes [Line Items] |  |  |
Deferred Tax Assets, Tax Credit Carryforwards, Research | $ 6,869 | $ 6,290 |
Excess Tax Benefit From Share Based Compensation Not Yet Recognized | 34,200 |  |
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | 4,752 | 7,358 | $ 13,714
Undistributed Earnings of Foreign Subsidiaries | 9,100 | 8,100 | 6,600
Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability, Undistributed Earnings of Foreign Subsidiaries | $ 3,200 | 2,800 | $ 2,300
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent | 34.00% |  |
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | $ 4,500 |  |
Internal Revenue Service (IRS) [Member] |  |  |
Schedule of Income Taxes [Line Items] |  |  |
Operating Loss Carryforwards | 213,900 | 209,400 |
Deferred Tax Assets, Tax Credit Carryforwards, Research | $ 10,100 | 9,200 |
Operating Loss Carryforward Expiration Year | 2026 |  |
State and Local Jurisdiction [Member] |  |  |
Schedule of Income Taxes [Line Items] |  |  |
Operating Loss Carryforwards | $ 122,200 | 118,600 |
Deferred Tax Assets, Tax Credit Carryforwards, Research | $ 4,000 | $ 3,500 |
Operating Loss Carryforward Expiration Year | 2018 |  |
Tax Credit Carry forwards Expiration Date | 2033 |  |

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32621-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32632-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319 + Details
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319 + Details
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32698-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=75116654&loc=d3e32123-109318 + Details
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