Lease Commitments - Schedule of Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 52	$ 45
Lease, Cost [Abstract]
Amortization of lease assets	11	4
Interest on lease liabilities	8	3
Variable lease cost	10	6
Sublease income	(8)	(6)
Total lease cost	$ 73	$ 52