Financing Arrangement (Schedule Of Interest Expense Related To Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Financing Arrangement [Line Items]
Amortization of debt discount	$ (1)	$ 0	$ (2)
Amortization of debt issuance costs	(2)	(2)	(2)
Coupon interest expense	(41)	(42)	(42)
Interest Expense, Other	(1)	0	(1)
Total interest expense	$ (45)	$ (44)	$ (47)