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Equity (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Equity (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 10	$ 7	$ 28	$ 42
Share-based compensation liability		15		15
Income tax obligations	5		5
Restricted Stock Units (RSUs) And Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Non-cash stock-based compensation expense			12
Restricted Stock Units (RSUs) And Common Stock \| Restructuring Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Non-cash stock-based compensation expense		2		2
Performance Shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Non-cash stock-based compensation expense	$ 3	$ 1	6	2
Additional Paid-in Capital
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Non-cash stock-based compensation expense			$ 15	$ 27
Common Stock \| Class A Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares issued under the plan (in shares)			1,738,016	869,000
Shares issued under omnibus incentive plan (in shares)	7,428	17,000	185,115	273,000
Common Stock \| Class B Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares issued under the plan (in shares)			1,335,169