Equity Items - Summary of Reconciliation of Changes in Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Balance, beginning of period		$ 3,571	$ 3,406
Balance, end of period		$ 3,036	$ 3,571	$ 3,406
Cash dividends declared per common share		$ 1.10	$ 1.05	$ 0.95
Common Stock and Paid in Capital [Member]
Balance, beginning of period		$ 757	$ 947	$ 932
Common shares issued under stock incentive and other plans	[1]	13	10	15
Common shares purchased under repurchase program	[2]		(200)
Balance, end of period		770	757	947
Retained earnings [Member]
Balance, beginning of period		3,224	2,750	2,696
Adoption of new accounting pronouncements	[3]		34
Net income (loss)		(508)	505	114
Regular dividends		(67)	(65)	(60)
Balance, end of period		2,649	3,224	2,750
Accumulated other comprehensive income (loss) [Member]
Balance, beginning of period		(410)	(291)	(222)
Adoption of new accounting pronouncements	[3]		(34)
Unrealized translation gain (loss)		27	(80)	(82)
Net change in investment securities				13
Pension and postretirement obligation adjustment			(5)
Balance, end of period		$ (383)	$ (410)	$ (291)

[1] Common shares issued were 391,180, 336,188 and 360,468 for 2020, 2019 and 2018, respectively

[2] Common shares repurchased were 2,637,054 for 2019

[3] Represents the cumulative-effect adjustment related to the adoption of the new guidance related to the accounting for equity securities and tax effects of intercompany transfers during fiscal 2019. See Note A for more information.