Summary of Significant Accounting Policies Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Jan. 01, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Other Non-current Assets	$ 434	$ 352
Accounts Receivable, Net, Current		1,051	$ 1,081
Accounts Receivable, Net of Allowance for Uncollectible Accounts of $123 in 2018 and $156 in 2017	1,103	$ 1,130
VENEZUELA | Revenue Recognition [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Effect of Change in Accounting Estimate	230
Other Non-current Assets	158
Accounts Receivable, Net of Allowance for Uncollectible Accounts of $123 in 2018 and $156 in 2017	$ 72