Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Line Items]
Income Tax Expense (Benefit)			$ (1,531)	$ 60	$ 406
Gross unrecognized tax benefits			983	417	$ 457	$ 389
Amount of unrecognized tax benefits that would affect the effective tax rate			722
Combined amount of accrued interest and penalties related to uncertain tax positions			34	17
Deferred Tax Assets, Valuation Allowance			288	162
Deferred Tax Assets, Gross			2,328	296
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 630	$ 1,170	1,760
Deferred Tax Assets, Net			1,902	33
Decrease in Unrecognized Tax Benefits is Reasonably Possible			25
Unrecognized Tax Benefits, Period Increase (Decrease)			148
Deferred Tax Asset, Intra-entity Transfer, Asset Other than Inventory			$ 1,818	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	21.00%	31.50%
Amount of foreign earnings that is not permanently reinvested (available for repatriation without a material cost)			$ 2,700
State [Member]
Income Tax Disclosure [Line Items]
Net operating Loss Carryforwards			1,500
Net operating loss attributable to various acquired companies			5
Tax credit carry forwards			131
Reduction in Taxes [Member]
Income Tax Disclosure [Line Items]
Income Tax Expense (Benefit)			80
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			393
Decrease in Unrecognized Tax Benefits is Reasonably Possible			541
Foreign Tax Authority [Member]
Income Tax Disclosure [Line Items]
Tax credit carry forwards			5
Cash, Cash Equivalents, and Short-term Investments			4,400
Swiss Federal Tax Administration (FTA) [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Assets, Valuation Allowance			131
Deferred Tax Assets, Net			$ 1,840