Derivatives - Additional Information (Detail) - Cross Currency Swaps [Member] - USD ($)	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Derivative [Line Items]
Fair value of swaps, net liability	$ 14,000,000	$ 1,000,000
Net Investment Hedge [Member]
Derivative [Line Items]
Notional Amount	250,000,000
Cumulative gain (loss) related to swaps	$ (12,000,000)	$ 2,000,000
Net Investment Hedge [Member] | Fixed Rate Debt [Member]
Derivative [Line Items]
Derivative Instruments Frequency of Cash Settlements	semi-annually