Equity Incentive Plans, Stock Options Outstanding (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Option shares outstanding beginning balance (in shares)	684,299	573,611	2,269,803
Options granted (in shares)	244	27,654	0
Options assumed upon acquisition (in shares)	604,900	666,586
Options exercised (shares)	(221,987)	(477,618)	(1,675,663)
Options canceled (in shares)	(153,948)	(105,934)	(20,529)
Option shares outstanding ending balance (in shares)	913,508	684,299	573,611
Option shares outstanding beginning balance (in dollars per share)	$ 28.41	$ 24.75	$ 25.58
Options granted (in dollars per shares)	41.09	46.66	0.00
Options assumed upon acquisition (in dollars per share)	35.03	29.33
Options exercised (in dollars per share)	25.30	26.42	25.91
Options canceled (in dollars per share)	31.52	28.17	22.78
Option shares outstanding ending balance (in dollars per share)	33.00	$ 28.41	$ 24.75
Closing price of company's common stock related to calculation of aggregate intrinsic value of stock options (in dollars per share)	$ 48.20
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Total intrinsic value of options exercised related to stock incentive plans	$ 4.7	$ 9.6	$ 25.5
Aggregate intrinsic value of options outstanding related to stock incentive plans	13.9
Aggregate intrinsic value of options exercisable related to stock incentive plans	$ 8.8
Exercisable number of option shares (in shares)	553,844	283,133
Weighted average exercise price per share of exercisable options (in dollars per share)	$ 32.33	$ 26.90
Weighted average fair value per share of stock options granted	$ 8.85	$ 9.00