Stock Plans 4 (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Stock option activity roll-forward
Number of shares, Outstanding beginning balance	6.0	5.8	8.0
Weighted average exercise price, Outstanding beginning balance (in dollars per share)	$ 25.17	$ 23.52	$ 23.03
Number of shares, Granted	1.7	1.8	0.6
Weighted average exercise price, Granted (in dollars per share)	$ 27.86	$ 24.39	$ 21.89
Number of shares, Exercised	(3.5)	(1.2)	(1.8)
Weighted average exercise price, Exercised (in dollars per share)	$ 25.06	$ 17.17	$ 20.79
Number of shares, Expired or terminated	(0.5)	(0.4)	(1.0)
Weighted average exercise price, Expired or terminated (in dollars per share)	$ 25.95	$ 22.09	$ 23.46
Number of shares, Outstanding ending balance	3.7	6.0	5.8
Weighted average exercise price, Outstanding ending balance (in dollars per share)	$ 26.13	$ 25.17	$ 23.52
Options exercisable
Number of shares, Options exercisable	0.7	3.7	4.7
Weighted average exercise price, Options exercisable (in dollars per share)	$ 26.07	$ 26.18	$ 24.24