Shareholders' Equity - Changes in Certain Components of Shareholders' Equity (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
	Mar. 17, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Begging balance					$ 5,053					$ 5,053
Beginning balance (shares)					(140,770,158)					(140,770,158)
Net Income		$ 181	$ 62	$ 216	$ 236	$ 301	$ 326	$ 287	$ 271	$ 695	$ 1,185	$ 1,293
Number of shares issued, in acquisition (shares)	15,900,000
Ending balance		$ 7,164				$ 5,053				$ 7,164	$ 5,053
Ending balance (shares)		(121,966,516)				(140,770,158)				(121,966,516)	(140,770,158)
Common Stock Issued at Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Begging 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]
Begging balance					2,198				2,068	2,198	2,068	1,920
Net Income										0	0	0
Share-based compensation and other plans, net										30	19	50
Share-based compensation										164	111	98
Acquisitions										2,083
Ending balance		4,475				2,198				4,475	2,198	2,068
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Begging balance					12,105				11,342	12,105	11,342	10,435
Net Income										695	1,185	1,293
Cash dividends, common										(485)	(421)	(386)
Share-based compensation and other plans, net										(2)
Ending balance		12,314				12,105				12,314	12,105	11,342
Deferred Compensation
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Begging balance					19				19	19	19	19
Net Income										0	0	0
Share-based compensation and other plans, net										1
Ending balance		20				19				20	19	19
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Begging balance					$ (8,601)				$ (8,204)	$ (8,601)	$ (8,204)	$ (7,769)
Beginning balance (shares)					(140,770,000)				(138,663,000)	(140,770,000)	(138,663,000)	(135,751,000)
Share-based compensation and other plans, net										$ (6)	$ 3	$ 15
Share-based compensation plans, net (shares)										2,839,000	1,431,000	2,537,000
Common stock held in trusts, net (shares)										5,000	36,000	36,000
Repurchase of common stock (shares)										0	(3,574,000)	(5,485,000)
Repurchase of common stock										$ 0	$ (400)	$ (450)
Acquisitions										$ 368
Number of shares issued, in acquisition (shares)										15,959,000
Ending balance		$ (8,239)				$ (8,601)				$ (8,239)	$ (8,601)	$ (8,204)
Ending balance (shares)		(121,967,000)				(140,770,000)				(121,967,000)	(140,770,000)	(138,663,000)