Stock-Based Compensation (Schedule Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Options, Outstanding, Beginning Balance	1,375
Options, Granted	1
Options, Exercised	(95)
Options, Forfeited, cancelled or expired		0
Options, Outstanding, Ending Balance	1,281	1,375
Options, Vested and expected to vest	1,281
Options, Exercisable	1,281
Weighted-average exercise price of options outstanding, beginning balance	$ 30.63
Weighted-average exercise price of options granted during period	94.86
Weighted-average exercise price of options exercised during the period	28.04
Weighted-average exercise price of options forfeited, cancelled or expired during the period		$ 0
Weighted-average exercise price of options outstanding, ending balance	30.89	$ 30.63
Weighted-average exercise price of options vested and expected to vest	30.89
Weighted-average exercise price of options exercisable	$ 30.89
Weighted-average remaining contractual term of options outstanding	4 years 7 months 2 days
Weighted-average remaining contractual term of options vested and expected to vest	4 years 7 months 2 days
Weighted-average remaining contractual term of options exercisable	4 years 7 months 2 days
Aggregate intrinsic value of options outstanding	$ 90
Aggregate intrinsic value of options vested and expected to vest	90
Aggregate intrinsic value of options exercisable	$ 90