Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 14,720	$ 16,487
Cash, cash equivalents, restricted cash and restricted cash equivalents	18,323	19,799	$ 18,055	$ 19,171
U.S. litigation escrow
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	1,144	894
Customer collateral
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	2,284	2,260
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	$ 175	$ 158