Share-Based Compensation - Compensation Cost Relating to Share-Based Payments (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	$ 245	$ 265	$ 332
Income tax benefit recognized	57	62	79
Cost of products sold
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	40	37	36
Selling and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	150	145	136
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	34	32	29
Acquisitions and other restructurings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost relating to share-based payments	$ 20	$ 50	$ 130