Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Income Taxes, Additional Information [Line Items]
Effective income tax rate	25.00%	44.00%
Ireland statutory income tax rate		12.50%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 30	$ 76
Gross tax effected unrecognized tax benefits			$ 2,451
Amount of unrecognized tax benefits which may impact effective tax rate			2,121
Total net accrued interest, net of tax benefit			$ 181
Income Tax Examination, Penalties and Interest Accrued	20
Restructuring and impairment costs	111	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Restructuring Charges, Amount	(16)
2020 Restructuring Plan
Income Taxes, Additional Information [Line Items]
Restructuring and impairment costs	111
2020 Restructuring Plan | Continuing Operations
Income Taxes, Additional Information [Line Items]
Restructuring and impairment costs	111
Global Products | 2020 Restructuring Plan
Income Taxes, Additional Information [Line Items]
Restructuring and impairment costs	$ 87
IRELAND
Income Taxes, Additional Information [Line Items]
Ireland statutory income tax rate	12.50%	12.50%