Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Mar. 31, 2020
Income Tax Footnote Disclosure [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount				$ 41
Gross unrecognized tax benefits	$ 563		$ 90	$ 563			$ 983
Effective Income Tax Rate Reconciliation, Percent	14.00%	8.00%		11.00%	(140.00%)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				21.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ 630
Deferred Tax Asset, Intra-entity Transfer, Asset Other than Inventory			$ 1,170
Deferred Tax Asset, Period Of Reversal			20 years
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions				$ 5
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions				(441)
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions				35
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				(2)
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations				(24)
Unrecognized Tax Benefits Changes Resulting From Foreign Currency Translation				$ 7
Pro Forma [Member]
Income Tax Footnote Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Percent		16.00%			14.00%
Reclassification, Other [Member]
Income Tax Footnote Disclosure [Line Items]
Taxes Payable, Current						$ 80