Stock Plans 8 (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Restricted Stock Awards (RSAs)
Summary of RSA and RSU activity under the Plans
Shares, Outstanding beginning balance	4.3	5.0	5.7
Weighted average grant date fair value, Outstanding beginning balance (in dollars per share)	$ 26.38	$ 24.98	$ 22.41
Shares, Granted	3.1	2.7	3.5
Weighted average grant date fair value, Granted (in dollars per share)	$ 28.97	$ 27.06	$ 26.21
Shares, Released	(2.2)	(2.6)	(3.6)
Weighted average grant date fair value, Released (in dollars per share)	$ 26.36	$ 24.49	$ 22.22
Shares, Forfeitures	(0.9)	(0.8)	(0.6)
Weighted average grant date fair value, Forfeitures (in dollars per share)	$ 27.79	$ 26.14	$ 24.69
Shares, Outstanding ending balance	4.3	4.3	5.0
Weighted average grant date fair value, Outstanding ending balance (in dollars per share)	$ 27.99	$ 26.38	$ 24.98
Restricted Stock Units (RSUs)
Summary of RSA and RSU activity under the Plans
Shares, Outstanding beginning balance	1.4	1.4	1.2
Weighted average grant date fair value, Outstanding beginning balance (in dollars per share)	$ 24.47	$ 23.28	$ 21.91
Shares, Granted	0.8	0.7	0.9
Weighted average grant date fair value, Granted (in dollars per share)	$ 26.99	$ 25.45	$ 23.72
Shares, Released	(0.6)	(0.6)	(0.6)
Weighted average grant date fair value, Released (in dollars per share)	$ 24.64	$ 23.01	$ 21.03
Shares, Forfeitures	(0.2)	(0.1)	(0.1)
Weighted average grant date fair value, Forfeitures (in dollars per share)	$ 25.59	$ 24.41	$ 23.38
Shares, Outstanding ending balance	1.4	1.4	1.4
Weighted average grant date fair value, Outstanding ending balance (in dollars per share)	$ 25.74	$ 24.47	$ 23.28