[Line Items] for Change in Tax Legislation and Statutory Tax Rates [Table]

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Maximum potential noncash impact for Swiss tax TRAF matter

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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Income Taxes Changes in Tax Legislation and Statutory Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Change in Tax Legislation and Statutory Tax Rates [Line Items]
Income tax provision					$ 233	$ (197)	$ (322)
Ireland statutory rate					12.50%	12.50%	12.50%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount					$ 0	$ 108	$ 0
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 139		$ 75	$ 101
Maximum potential noncash impact for Swiss tax TRAF matter					$ 100
Remeasurement of U.S. deferred tax assets and liabilities [Member]
Change in Tax Legislation and Statutory Tax Rates [Line Items]
Income tax provision		$ 101				108
Transition Tax on Deemed Repatriated Earnings [Member]
Change in Tax Legislation and Statutory Tax Rates [Line Items]
Income tax provision		$ 305				$ 216
United States
Change in Tax Legislation and Statutory Tax Rates [Line Items]
Ireland statutory rate					21.00%	24.50%