Leases Expense (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020
Leases [Abstract]
Operating lease expense	$ 53	$ 106
Variable lease expense	$ 5	10
Cash paid for operating leases, operating cash flows		101
Operating lease right-of-use asset additions		$ 123