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

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Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Convertible Senior Notes - Narrative (Detail) - USD ($) $ in Millions	Apr. 30, 2022	Sep. 30, 2019	Jun. 30, 2018
2024 Notes
Debt Instrument
Debt instrument, principal amount		$ 350
Private Offering \| 2024 Notes
Debt Instrument
Debt instrument, principal amount		$ 350
Debt instrument, interest rate		0.00%
Private Offering \| 2023 Notes
Debt Instrument
Debt instrument, principal amount	$ 335		$ 300
Debt instrument, interest rate			0.00%
Overallotment option \| 2023 Notes
Debt Instrument
Debt instrument, principal amount			$ 35