Stock-Based Compensation (Schedule Of Stock Option Activity) (Details) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Options, Outstanding, Beginning Balance | shares	2,377
Options, Granted | shares	2
Options, Exercised | shares	(744)
Options, Forfeited, cancelled or expired | shares	(2)
Options, Outstanding, Ending Balance | shares	1,633
Options, Vested and expected to vest | shares	1,633
Options, Exercisable | shares	1,553
Weighted-average exercise price of options outstanding, beginning balance | $ / shares	$ 33.35
Weighted-average exercise price of options granted during period | $ / shares	105.99
Weighted-average exercise price of options exercised during the period | $ / shares	40.47
Weighted-average exercise price of options forfeited, cancelled or expired during the period | $ / shares	46.31
Weighted-average exercise price of options outstanding, ending balance | $ / shares	30.19
Weighted-average exercise price of options vested and expected to vest | $ / shares	30.19
Weighted-average exercise price of options exercisable | $ / shares	$ 30.40
Weighted-average remaining contractual term of options outstanding	5 years 10 months 29 days
Weighted-average remaining contractual term of options vested and expected to vest	5 years 10 months 29 days
Weighted-average remaining contractual term of options exercisable	5 years 10 months 25 days
Aggregate intrinsic value of options outstanding | $	$ 143
Aggregate intrinsic value of options vested and expected to vest | $	143
Aggregate intrinsic value of options exercisable | $	$ 136