Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures
Gain from Components Excluded from Assessment of Cash Flow Hedge Effectiveness	$ 25	$ 10
Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures
Foreign Currency Forward And Option Contracts Maximum Maturity Period	18 months
Not Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures
Foreign Currency Forward And Option Contracts Maximum Maturity Period	3 months