Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Accumulated other comprehensive income [Roll Forward]
Beginning balance			$ 8,770
Ending balance	$ 8,460		8,460
Accumulated other comprehensive income (loss)	(1,092)	$ (1,575)	(1,092)	$ (1,575)	$ (1,019)
Foreign currency translation [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(214)	(655)	(369)	(812)
Other comprehensive income (loss) before reclassifications	(273)	75	(101)	(153)
Reclassified to gain/loss on sale of businesses	0	0	(17)	385
Ending balance	(487)	(580)	(487)	(580)
Pension and post retirement [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(617)	(1,042)	(662)	(1,162)
Amortization of deferred actuarial losses into earnings	22	35	67	105
Reclassified to gain/loss on sale of businesses	0	0	0	50
Ending balance	(595)	(1,007)	(595)	(1,007)
Cash Flow Hedges [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	4	7	12	(25)
Deferral of gains (losses) arising during the period	(13)	7	(13)	30
Reclassification of realized (gains) losses to sales and cost of sales	(1)	(2)	(9)	7
Ending balance	$ (10)	$ 12	$ (10)	$ 12