Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	$ 7,618	$ 8,128
Stockholders' equity, Ending balance	8,770	7,618	$ 8,128
Accumulated other comprehensive income (loss)	(1,019)	(1,999)	(1,617)
Foreign currency translation
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(812)	(622)	171
Other comprehensive income (loss)	58	(190)	(793)
Reclassified to gain/loss on sale of businesses	385	0	0
Stockholders' equity, Ending balance	(369)	(812)	(622)
Pension and postretirement
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(1,162)	(952)	(746)
Actuarial gains (losses) deferred during the period	315	(310)	(315)
Amortization of deferred actuarial losses into earnings	135	100	109
Reclassified to gain/loss on sale of businesses	50	0	0
Stockholders' equity, Ending balance	(662)	(1,162)	(952)
Actuarial gains (losses) deferred during the period, tax	(170)	159	192
Amortization of deferred actuarial (gains) losses into earnings, tax	(75)	(59)	(59)
Cash flow hedges
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(25)	(43)	0
Gains (Losses) deferred during the period	34	(30)	(66)
Reclassifications of realized (gains) losses to sales and cost of sales	3	48	23
Stockholders' equity, Ending balance	12	(25)	(43)
Gains (losses) deferred during the period, tax	(21)	17	38
Reclassification of (gains) losses to sales and cost of sales, tax	$ (2)	$ (28)	$ (13)