Accounting for Share-Based Compensation 5 (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Restricted Stock Awards (RSAs) [Member]
Summary of RSAs and RSUs granted
Number of shares granted	0	[1]	0	[1]	2.7		3.6
Weighted average grant date fair value	$ 30.39	[2]	$ 25.54	[2]	$ 27.01	[2]	$ 26.23	[2]
Restricted Stock Units (RSUs) [Member]
Summary of RSAs and RSUs granted
Number of shares granted	0	[1]	0	[1]	0.8		0.7
Weighted average grant date fair value	$ 30.13	[3]	$ 23.63	[3]	$ 25.37	[3]	$ 24.29	[3]

[1] Less than 0.1 million.

[2] The fair value is based on the quoted market value of the Company's common stock on the grant date.

[3] The fair value is based on the quoted market value of the Company's common stock on the grant date reduced by the present value of dividends expected to be paid on the Company's common stock prior to vesting of the RSUs, which is calculated using a risk-free interest rate.