Equity Incentive Plans, Stock Options Outstanding (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Option shares outstanding beginning balance (in shares)	2,269,803	3,360,997	5,496,924
Options granted (in shares)	0	0	0
Options assumed upon acquisition (in shares)		827,707
Options exercised (shares)	(1,675,663)	(1,638,548)	(2,129,260)
Options canceled (in shares)	(20,529)	(280,353)	(6,667)
Option shares outstanding ending balance (in shares)	573,611	2,269,803	3,360,997
Option shares outstanding beginning balance (in dollars per share)	$ 25.58	$ 25.00	$ 25.21
Options granted (in dollars per shares)	$ 0.00	$ 0.00	$ 0.00
Options assumed upon acquisition (in dollars per share)		$ 19.32
Options exercised (in dollars per share)	$ 25.91	$ 22.19	$ 25.53
Options canceled (in dollars per share)	$ 22.78	$ 19.90	$ 25.05
Option shares outstanding ending balance (in dollars per share)	$ 24.75	$ 25.58	$ 25.00
Closing price of company's common stock related to calculation of aggregate intrinsic value of stock options (in dollars per share)	$ 47.76
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	$ 25.5	$ 19.0	$ 26.7
Aggregate intrinsic value of options outstanding related to stock incentive plans	13.2
Aggregate intrinsic value of options exercisable related to stock incentive plans	$ 12.4
Exercisable number of option shares (in shares)	543,435	1,922,644
Weighted average exercise price per share of exercisable options (in dollars per share)	$ 25.03	$ 26.77