Share-Based Compensation - Compensation Cost Relating to Share-Based Payments (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	$ 265	$ 332	$ 177
Income tax benefit recognized	62	79	61
Cost of products sold
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	37	36	30
Selling and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	145	136	113
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	32	29	24
Acquisitions and other restructurings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	$ 50	$ 130	$ 10