Common Stock and Stockholders' Equity - Schedule of Assumptions Used to Estimate Fair Value of Stock Options Granted and ESPP Shares to be Issued (Detail)	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years	6 years
Dividend yield	0.00%	0.00%	0.00%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Dividend yield	0.00%	0.00%	0.00%
Minimum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)			5 years
Expected volatility	41.00%	42.00%	46.00%
Risk-free interest rate	2.27%	1.86%	0.21%
Minimum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	37.00%	29.00%	37.00%
Risk-free interest rate	2.23%	1.16%	0.46%
Maximum \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)			6 years
Expected volatility	42.00%	44.00%	47.00%
Risk-free interest rate	3.06%	2.74%	2.17%
Maximum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	53.00%	30.00%	44.00%
Risk-free interest rate	2.50%	1.82%	0.67%

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 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

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- Definition

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

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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.

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No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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