v3.7.0.1

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions | 12 Months Ended |
--- | --- | ---
Apr. 30, 2017 USD ($) $ / shares shares | Apr. 30, 2016 USD ($) $ / shares shares | Apr. 30, 2015 USD ($) $ / shares shares | Aug. 02, 2016 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of non-vested shares | 6,428,000 | 4,967,000 | 3,488,000 |
Maximum stock option exercise price | $ / shares |  |  |  | $ 6.11
Number of eligible participants |  |  |  | 113
Number of options exchanged |  |  |  | 599,517
Weighted average exercise price of options canceled and exchanged | $ / shares |  |  |  | $ 9.25
Replacement options granted |  |  |  | 241,399
Replacement option exercise price | $ / shares |  |  |  | $ 4.14
Restricted shares |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | 2 years 2 months 18 days |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $ | $ 10.5 | $ 8.5 | $ 6.2 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $ | $ 20.0 |  |  |
Stock Options |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 5,548,000 | 6,688,000 | 5,093,000 |
Options granted | 749,000 | 2,947,000 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares | $ 1.36 | $ 2.06 | $ 3.47 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value | $ | $ 0.3 | $ 0.4 | $ 4.5 |
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options | $ | 0.4 | 0.9 | 5.2 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value | $ | 4.3 | $ 4.2 | $ 6.1 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options | $ | $ 3.4 |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | 2 years 2 months 25 days |  |  |
Performance Stock Options (PSOs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 839,000 | 0 |  |
Options granted | 2,867,000 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ / shares | $ 1.45 |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options | $ | $ 0.5 |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | 3 years 1 month 2 days |  |  |
Two Thousand Five Stock Option Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | 25.00% |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 475,879 |  |  |
Common Stock, Capital Shares Reserved for Future Issuance | 475,879 |  |  |
2012 Equity incentive plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | 25.00% |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 5,910,892 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | 110.00% |  |  |
Number of non-vested shares | 6,208,958 |  |  |
Options granted | 6,692,386 |  |  |
Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | 85.00% |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | 2,820,145 |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Amount Held For Future Purchases | $ | $ 0.3 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award | 613,504 |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Per Share Weighted Average Price of Shares Purchased | $ / shares | $ 3.27 |  |  |

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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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