Shareholders' Equity - Changes in Certain Components of Shareholders' Equity (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
	Mar. 17, 2015	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					$ 7,164					$ 7,164
Beginning balance (shares)					(121,966,516)					(121,966,516)
Net Income		$ 19	$ 390	$ 338	$ 229	$ 181	$ 62	$ 216	$ 236	$ 976	$ 695	$ 1,185
Number of shares issued, in acquisition (shares)	15,900,000
Ending balance		$ 7,633				$ 7,164				$ 7,633	$ 7,164
Ending balance (shares)		(119,370,934)				(121,966,516)				(119,370,934)	(121,966,516)
Common Stock Issued at Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					333				333	$ 333	$ 333	333
Net Income										0	0	0
Ending balance		$ 333				$ 333				333	333	333
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					4,475				2,198	4,475	2,198	2,068
Net Income										0	0	0
Share-based compensation and other plans, net										27	30	19
Share-based compensation										191	164	111
Acquisitions											2,083
Ending balance		4,693				4,475				4,693	4,475	2,198
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					12,314				12,105	12,314	12,105	11,342
Net Income										976	695	1,185
Cash dividends, common										(562)	(485)	(421)
Share-based compensation and other plans, net										(1)	(2)
Ending balance		12,727				12,314				12,727	12,314	12,105
Deferred Compensation
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					20				19	20	19	19
Net Income										0	0	0
Share-based compensation and other plans, net										2	1
Ending balance		22				20				22	20	19
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance					$ (8,239)				$ (8,601)	$ (8,239)	$ (8,601)	$ (8,204)
Beginning balance (shares)					(121,967,000)				(140,770,000)	(121,967,000)	(140,770,000)	(138,663,000)
Share-based compensation and other plans, net										$ 26	$ (6)	$ 3
Share-based compensation plans, net (shares)										2,607,000	2,839,000	1,431,000
Common stock held in trusts, net (shares)										11,000	5,000	36,000
Repurchase of common stock (shares)												(3,574,000)
Repurchase of common stock												$ (400)
Acquisitions											$ 368
Number of shares issued, in acquisition (shares)											15,959,000
Ending balance		$ (8,212)				$ (8,239)				$ (8,212)	$ (8,239)	$ (8,601)
Ending balance (shares)		(119,371,000)				(121,967,000)				(119,371,000)	(121,967,000)	(140,770,000)