Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative
Gain from Components Excluded from Assessment of Cash Flow Hedge Effectiveness	$ 7		$ 14
Designated as Hedging Instrument [Member]
Derivative
Maximum Remaining Maturity of Foreign Currency Derivatives		18 months
Not Designated as Hedging Instrument [Member]
Derivative
Maximum Remaining Maturity of Foreign Currency Derivatives		3 months