Financing Arrangement (Schedule Of Interest Expense Related To Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Financing Arrangement [Line Items]
Amortization of debt discount	$ 0	$ (2)	$ (17)
Amortization of debt issuance costs	(2)	(2)	(3)
Coupon interest expense	(42)	(42)	(7)
Interest Expense, Other	0	(1)	(1)
Total interest expense	$ (44)	$ (47)	$ (28)