Equity Incentive Plans - Assumptions Used to Estimated Fair Value of Stock Options Granted (Details)	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility (in percentage)	54.80%
Expected stock price volatility, minimum (in percentage)		40.50%	40.70%
Expected stock price volatility, maximum (in percentage)		46.70%	44.10%
Risk-free interest rate, minimum	1.40%	2.40%	1.80%
Risk-free interest rate, maximum	2.00%	3.10%	2.60%
Dividend yield (in percentage)	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	2 years	6 years 7 days	6 years 7 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	7 years 3 months 7 days	6 years 29 days	6 years 29 days

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

+ Details

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- Definition

The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

Rate of weighted-average expected volatility for award under share-based payment arrangement.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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