Share-Based Compensation (Components of Share-Based Compensation Expense And Related Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2012		May 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 160		$ 167		$ 154
Tax benefit for share-based compensation expense	(55)	[1]	(59)	[1]	(55)	[1]
Share-based compensation expense, net of tax	105		108		99
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	88	[2]	109	[2]	97	[2]
PeRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized							1.0
Share-based compensation expense	38	[3]	23	[3]	24	[3]
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	22		24		23
Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized	21.0
Share-based compensation expense	$ 12		$ 11		$ 10
2013 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Authorized	30.0

[1] Income tax benefit is computed using the tax rates of applicable tax jurisdictions. Additionally, a portion of pre-tax compensation expense is not tax-deductible.

[2] This expense was primarily the result of PeRSUs awarded in prior years, which converted to RSUs due to the attainment of goals during the applicable years’ performance period.

[3] Represents estimated compensation expense for PeRSUs that are conditional upon attaining performance objectives during the current year’s performance period.