Financial Instruments - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019
Foreign exchange forward contracts | Cash flow hedge | Designated as hedging instrument
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Term of derivative contract		18 months
Aggregate notional amount	$ 69,000,000	$ 69,000,000	$ 110,000,000
Foreign currency option contracts, purchase risk
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Aggregate notional amount	68,000,000	$ 68,000,000	139,000,000
Foreign currency option contracts, translation risk
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Aggregate notional amount			28,000,000
Cross-currency swaps | Net investment hedge | Designated as hedging instrument
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Aggregate notional amount			$ 225,000,000	$ 225,000,000
Proceeds from settlement of swap contracts	11,000,000
Component of proceeds that was previously in net accrued interest receivable	$ 1,000,000