Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Right-of-use assets obtained in exchange for lease obligations:
Operating leases (non-cash activity)	$ 109	$ 79
Operating cash flows:
Cash paid for amounts included in the measurement of lease liabilities	$ 126	$ 125