Income Taxes (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended			15 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Tax benefit from restructuring foreign subsidiary			$ 103,000	$ 74,000	$ 53,000
Tax benefit from restructuring foreign subsidiary per share			$ 0.17	$ 0.12	$ 0.08
Federal statutory rate	35.00%	21.00%	21.00%	21.00%	24.50%
Net income tax expense (benefit), tax reform			$ 0	$ 0	$ 189
Net income tax expense (benefit), tax reform, per diluted share					$ (0.30)
Income tax expense (benefit), continuing operations, adjustment of deferred tax (asset) liability					$ (94)
Income tax expense (benefit) due to repatriation of foreign earnings and withholding taxes					(35)
Income tax benefit for repatriation of foreign earnings, prior periods					(130)
Income Tax [Line Items]
Payroll tax deferral from CARES Act			$ 48
Non-U.S. tax holiday tax rate reductions for certain foreign jurisdictions, expiration period in years			2 years
Unrecognized tax benefits that would impact effective tax rate			$ 163
Unrecognized tax benefits, income tax penalties and interest expense			1	4	2
Unrecognized tax benefits, income tax penalties and interest accrued			29	27
Income taxes paid			400	$ 650	$ 680
Amount of net operating losses, capital losses and tax credits recovering in the next 12 months			$ 126
Amount of net operating losses and tax credits expiring over the next 9 years			More than half
Net operating losses and tax credits, remaining to expire over next 9 years			$ 361
Scenario, Forecast [Member]
Income Tax [Line Items]
Payroll tax deferral from CARES Act						$ 75