Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended					9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Income Taxes, Additional Information [Line Items]
Effective income tax rate	1.00%			52.00%		20.00%	38.00%
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
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense						$ 55	$ 49
Restructuring and impairment costs	$ 610			$ 235		783	$ 235
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		$ 62
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount				199
Effective Income Tax Rate Reconciliation, Tax Contingency, Foreign, Amount				27
Mark-to-market gain (loss)	132
Release of tax indemnification reserve				226
Unrecognized Tax Benefit Decrease Resulting From Tax Audit Resolution	22	22
Income Tax Reconciliation, Restructuring and Impairment Charges	28	$ 4	16
Mark-to-market [Domain]
Income Taxes, Additional Information [Line Items]
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(34)
2020 Restructuring Plan
Income Taxes, Additional Information [Line Items]
Restructuring and impairment costs	$ 186		111			297
Global Products
Income Taxes, Additional Information [Line Items]
Impairment of Long-Lived Assets to be Disposed of			$ 15	235
Income Tax Reconciliation, Restructuring and Impairment Charges				$ 53
Global Products | 2020 Restructuring Plan
Income Taxes, Additional Information [Line Items]
Restructuring and impairment costs						$ 136
IRELAND
Income Taxes, Additional Information [Line Items]
Ireland statutory income tax rate	12.50%			12.50%		12.50%	12.50%