CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Deferred Compensation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update	$ 28			$ 28
Beginning balance at Sep. 30, 2018	8,003	$ 7	$ 3,379	7,011	$ (2,371)	$ 4	$ (27)
Beginning balance (in shares) at Sep. 30, 2018		563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	604			604
Other comprehensive income (loss), net of tax	13						13
Common stock dividends	(168)			(168)
Repurchases of common stock	(114)		31		(145)
Repurchases of common stock (in shares)		(3)
Future treasury stock purchases under accelerated stock repurchase agreement	(12)		(12)
Repurchases of common stock for income tax withholding on stock-based compensation	(8)				(8)
Common stock issued for stock-based compensation, including tax effects	0		(9)		9
Common stock issued for stock-based compensation, including tax effects (in shares)		1
Stock-based compensation	11		11
Ending balance at Dec. 31, 2018	8,357	$ 7	3,400	7,475	(2,515)	$ 4	(14)
Ending balance (in shares) at Dec. 31, 2018		561
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of Accounting Standards Update	(1)			(1)
Beginning balance at Sep. 30, 2019	$ 8,700	$ 7	3,452	8,580	(3,380)		41
Beginning balance (in shares) at Sep. 30, 2019	544	544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 379			379
Other comprehensive income (loss), net of tax	(23)						(23)
Common stock dividends	(168)			(168)
Repurchases of common stock	(143)				(143)
Repurchases of common stock (in shares)		(4)
Repurchases of common stock for income tax withholding on stock-based compensation	(12)				(12)
Common stock issued for stock-based compensation, including tax effects	0		(8)		8
Common stock issued for stock-based compensation, including tax effects (in shares)		1
Stock-based compensation	15		15
Ending balance at Dec. 31, 2019	$ 8,747	$ 7	$ 3,459	$ 8,790	$ (3,527)		$ 18
Ending balance (in shares) at Dec. 31, 2019	541	541