Leases - Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	7 years 6 months	7 years 6 months
Operating Lease, Weighted Average Discount Rate, Percent	2.30%	2.30%
Lease, Cost	$ 32	$ 65
Minimum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	25 years	25 years