Share-Based Compensation - Option Activity and Information about Options Outstanding (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Number of Options
Outstanding at beginning of period (in shares) | shares	4,791,045
Granted (in shares) | shares	208,264
Exercised (in shares) | shares	(1,116,857)
Canceled/forfeited (in shares) | shares	(85,832)
Outstanding at end of period (in shares) | shares	3,796,620
Vested or expected to vest at end of period (in shares) | shares	3,776,873
Vested and exercisable at end of period (in shares) | shares	3,132,123
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 28.55
Granted (in dollars per share) | $ / shares	34.68
Exercised (in dollars per share) | $ / shares	12.34
Canceled/forfeited (in dollars per share) | $ / shares	67.04
Outstanding at end of period (in dollars per share) | $ / shares	32.78
Vested or expected to vest at end of period (in dollars per share) | $ / shares	32.78
Vested and exercisable at end of period (in dollars per share) | $ / shares	$ 29.28
Weighted Average Remaining Contractual Life
Outstanding at end of period (in years)	2 years 7 months 18 days
Vested or expected to vest at end of period (in years)	2 years 7 months 18 days
Vested and exercisable at end of period (in years)	2 years 2 months 8 days
Aggregate Intrinsic Value
Outstanding at end of period | $	$ 124.6
Vested and exercisable at end of period | $	$ 112.8