Revenue - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Net revenue	$ 40,000	$ 35,926	$ 32,653
Revenue, remaining performance obligation, amount	4,900
Value-Added Services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Net revenue	$ 10,900	$ 8,800	$ 7,200
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (in percent)	50.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (in percent)	50.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period (in years)