Financing Arrangement (Schedule Of Interest Expense Related To Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Financing Arrangement [Line Items]
Amortization of debt discount	$ (2)	$ (17)	$ (22)
Amortization of debt issuance costs	(2)	(3)	(3)
Coupon interest expense	(42)	(7)	(5)
Interest Expense, Other	(1)	(1)	(1)
Total interest expense	$ (47)	$ (28)	$ (31)