Goodwill And Intangible Assets, Net (Information Regarding Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Sep. 30, 2013	Mar. 31, 2013
Intangible assets
Gross Carrying Amount	$ 3,308	$ 3,347
Accumulated Amortization	(1,158)	(1,077)
Net Carrying Amount	2,150	2,270
Customer lists [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	7 years
Gross Carrying Amount	1,794	1,761
Accumulated Amortization	(758)	(672)
Net Carrying Amount	1,036	1,089
Service agreements [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	17 years
Gross Carrying Amount	1,009	1,018
Accumulated Amortization	(145)	(114)
Net Carrying Amount	864	904
Trademarks and trade names [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	16 years
Gross Carrying Amount	205	208
Accumulated Amortization	(51)	(46)
Net Carrying Amount	154	162
Technology [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	4 years
Gross Carrying Amount	215	271
Accumulated Amortization	(166)	(207)
Net Carrying Amount	49	64
Other [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	6 years
Gross Carrying Amount	85	89
Accumulated Amortization	(38)	(38)
Net Carrying Amount	$ 47	$ 51