Leasing - Schedule of Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020
Leases [Abstract]
Operating Lease, Cost	$ 11	$ 22
Lease, Cost [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	1	1
Finance Lease, Interest Expense	1	2
Variable Lease, Cost	1	2
Sublease Income	(2)	(3)
Lease, Cost, Total	12	24
Operating cash flows from finance leases	1	2
Financing cash flow from finance leases	0	0
Leased assets obtained in exchange for operating leases	13	28
Leased assets obtained in exchange for finance leases	$ 18	$ 18