Stock-Based Compensation (Summary of Stock Option Activity) (Details) (Stock Option [Member], USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of period, Number Of Stock Options	5,052,016	6,584,482	6,885,586
Granted, Number Of Stock Options	959,700	966,300	995,038
Exercised, Number Of Stock Options	(817,016)	(2,423,265)	(1,253,672)
Forfeited, Number Of Stock Options	(90,276)	(75,501)	(42,470)
Outstanding at the end of period, Number Of Stock Options	5,104,424	5,052,016	6,584,482
Vested or expected to vest as of March 31, 2014, Number Of Stock Options	5,092,587
Exercisable as of March 31, 2014, Number Of Stock Options	2,934,768
Outstanding at the beginning of period, Weighted-Average Exercise Price Per Share	$ 60.26	$ 47.08	$ 41.11
Granted, Weighted-Average Exercise Price Per Share	$ 102.96	$ 91.52	$ 66.39
Exercised, Weighted-Average Exercise Price Per Share	$ 47.38	$ 36.67	$ 29.27
Forfeited, Weighted-Average Exercise Price Per Share	$ 85.04	$ 67.86	$ 57.35
Outstanding at the end of period, Weighted-Average Exercise Price Per Share	$ 69.91	$ 60.26	$ 47.08
Vested or expected to vest as of March 31, 2014, Weighted-Average Exercise Price Per Share	$ 69.83
Exercisable at March 31, 2014, Weighted-Average Exercise Price Per Share	$ 56.15
Outstanding at the end of period, Aggregate Intrinsic Value	$ 186,816	$ 196,527	$ 275,849
Vested or expected to vest as of March 31, 2014, Aggregate Intrinsic Value	186,794
Exercisable as of March 31, 2014, Aggregate Intrinsic Value	$ 147,781