CONVERTIBLE SENIOR NOTES - Components of Notes (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2018
2023 Convertible Senior Notes
Debt Instrument [Line Items]
Net carrying amount	$ 498,378	$ 490,222
Convertible Debt \| 2023 Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount	575,000	575,000	$ 575,000
Unamortized discount	(72,573)	(80,298)
Unamortized debt issuance cost	(4,049)	(4,480)
Carrying amount of equity component	$ 148,598	$ 148,598
Effective interest rate	6.62%
Payments of offering costs	$ (3,000)		$ (3,000)
Convertible Debt \| 2026 Convertible Senior Notes
Debt Instrument [Line Items]
Principal amount	750,000
Unamortized discount	(227,723)
Unamortized debt issuance cost	(26,018)
Net carrying amount	$ 496,259
Effective interest rate	705.00%

Face (par) amount of debt instrument at time of issuance.

No definition available.

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- Definition

Debt Instrument, Convertible, Carrying Amount of Equity Component, Excluding Equity Issuance Costs

+ References

No definition available.

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- Definition

Debt Instrument, Convertible, Transaction Costs Attributable to Equity Component

+ References

No definition available.

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- Definition

Carrying amount of long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months or greater than the normal operating cycle, if longer. The debt is convertible into another form of financial instrument, typically the entity's common stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

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-Topic 835
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-Section 45
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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

Amount, after accumulated amortization, of debt discount.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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