Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Related Party Transactions [Abstract]
Net sales to related parties	$ 88	$ 110	$ 180	$ 209
Purchases from related parties	177	$ 173	350	$ 310
Accounts receivable due from related parties	83		83		$ 91
Accounts payable due to related parties	$ 111		$ 111		$ 102