Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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STOCK-BASED COMPENSATION - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	May 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock-based compensation expense		$ 144,066,000	$ 127,540,000	$ 144,066,000	$ 127,540,000
2017 Repurchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized repurchase amount						$ 25,000,000.0
Remaining authorized repurchase amount		$ 7,100,000		$ 7,100,000
Stock repurchased during period (in shares)		0	0	0	0
Employee Stock Purchase Plan \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued under employee stock purchase plan (in shares)	329,430
Unamortized stock-based compensation expense		$ 2,900,000		$ 2,900,000
Weighted average period of recognition for unrecognized compensation expense				6 months 25 days
Number of shares reserved for future issuance (in shares)		3,252,882		3,252,882