Financing Arrangement (Schedule Of Interest Expense Related To Notes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Debt Instruments [Abstract]
Amortization of debt discount	$ 0	$ 0	$ 0	$ (2)
Amortization of debt issuance costs	0	(1)	(1)	(2)
Coupon interest expense	(10)	(10)	(31)	(31)
Interest Expense, Other	0	(1)		(1)	$ 0
Total interest expense	$ (10)	$ (12)	$ (32)	$ (36)