Goodwill And Intangible Assets, Net (Information Regarding Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Dec. 31, 2011	Mar. 31, 2011
Intangible assets
Gross Carrying Amount	$ 2,162	$ 2,136
Accumulated Amortization	(821)	(680)
Net Carrying Amount	1,341	1,456
Customer Lists [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P7Y
Gross Carrying Amount	1,074	1,057
Accumulated Amortization	(526)	(444)
Net Carrying Amount	548	613
Service Agreements [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P17Y
Gross Carrying Amount	701	723
Accumulated Amortization	(46)	(11)
Net Carrying Amount	655	712
Trademarks And Trade Names [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P13Y
Gross Carrying Amount	77	76
Accumulated Amortization	(36)	(31)
Net Carrying Amount	41	45
Technology [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P4Y
Gross Carrying Amount	234	204
Accumulated Amortization	(185)	(170)
Net Carrying Amount	49	34
Other [Member]
Intangible assets
Weighted Average Remaining Amortization Period (years)	P8Y
Gross Carrying Amount	76	76
Accumulated Amortization	(28)	(24)
Net Carrying Amount	$ 48	$ 52