Income Taxes Significant Components of Company's Income Tax Provision from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Components of Income Tax [Line Items]
Tax expense at Ireland statutory rate		$ 327	$ 113	$ 132
U.S. state income tax, net of federal benefit		34	8	15
Income subject to the U.S. federal tax rate		3	(92)	(110)
Income subject to rates different than the statutory rate		30	99	38
Reserve and valuation allowance adjustments		66	(70)	(284)
Intercompany intellectual property transfer	$ 417	417	0	0
Restructuring and impairment costs		(9)	50	(24)
Income tax provision		$ 868	$ 108	$ (233)
Ireland statutory rate				12.50%
Effective Income Tax Rate Reconciliation, Percent		33.00%	12.00%
IRELAND
Components of Income Tax [Line Items]
Ireland statutory rate		12.50%