Goodwill and Intangible Assets, Net (Information Regarding Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Intangible assets
Gross Carrying Amount	$ 3,347	$ 2,615
Accumulated Amortization	(1,077)	(865)
Net Carrying Amount	2,270	1,750
Customer Lists [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P8Y
Gross Carrying Amount	1,761	1,081
Accumulated Amortization	(672)	(554)
Net Carrying Amount	1,089	527
Service Agreements [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P17Y
Gross Carrying Amount	1,018	1,022
Accumulated Amortization	(114)	(52)
Net Carrying Amount	904	970
Trademarks And Trade Names [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P16Y
Gross Carrying Amount	208	192
Accumulated Amortization	(46)	(38)
Net Carrying Amount	162	154
Technology [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P4Y
Gross Carrying Amount	271	244
Accumulated Amortization	(207)	(190)
Net Carrying Amount	64	54
Other Intangible Assets [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P6Y
Gross Carrying Amount	89	76
Accumulated Amortization	(38)	(31)
Net Carrying Amount	$ 51	$ 45