Condensed Consolidated Statement of Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Noncontrolling Interest
Beginning balance (in shares) at Sep. 30, 2016		130.2
Beginning balance at Sep. 30, 2016	$ 2,084	$ 1	$ 1,506	$ 3,327	$ (1,898)	$ (858)	$ 6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	145			145
Other comprehensive income	(8)				(8)
Cash dividends	(43)			(43)
Shares issued:
Exercise of stock options (in shares)		0.3
Exercise of stock options	15		(2)			17
Vesting of performance shares and restricted stock units (in shares)		0.1
Vesting of performance shares and restricted stock units	(7)		(12)			5
Employee stock purchase plan (in shares)		0.0
Employee stock purchase plan	3		1			2
Employee savings plan (in shares)		0.1
Employee savings plan	13		3			10
Stock-based compensation	6		6
Ending balance (in shares) at Dec. 31, 2016		130.7
Ending balance at Dec. 31, 2016	2,208	$ 1	1,502	3,429	(1,906)	(824)	6
Beginning balance (in shares) at Sep. 30, 2016		130.2
Beginning balance at Sep. 30, 2016	2,084	$ 1	1,506	3,327	(1,898)	(858)	6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	(8)
Ending balance (in shares) at Sep. 30, 2017		162.9
Ending balance at Sep. 30, 2017	6,050	$ 2	4,559	3,838	(1,575)	(781)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	280			280
Other comprehensive income	27				27
Cash dividends	(54)			(54)
Shares issued:
Exercise of stock options (in shares)		0.8
Exercise of stock options	47		(5)			52
Vesting of performance shares and restricted stock units (in shares)		0.1
Vesting of performance shares and restricted stock units	(11)		(14)			3
Employee savings plan (in shares)		0.1
Employee savings plan	13		7			6
Stock-based compensation	9		9
Ending balance (in shares) at Dec. 31, 2017		163.9
Ending balance at Dec. 31, 2017	$ 6,361	$ 2	$ 4,556	$ 4,064	$ (1,548)	$ (720)	$ 7