Goodwill and Intangible Assets, Net (Information Regarding Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 5,204	$ 6,201
Accumulated Amortization	(1,763)	(1,330)
Net Carrying Amount	3,441us-gaap_FiniteLivedIntangibleAssetsNet	4,871us-gaap_FiniteLivedIntangibleAssetsNet
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	8 years
Gross Carrying Amount	2,683	3,235
Accumulated Amortization	(1,116)	(863)
Net Carrying Amount	1,567	2,372
Service Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	15 years
Gross Carrying Amount	957	995
Accumulated Amortization	(215)	(173)
Net Carrying Amount	742	822
Pharmacy Licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	26 years
Gross Carrying Amount	874	1,219
Accumulated Amortization	(65)	(11)
Net Carrying Amount	809	1,208
Trademarks and Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	15 years
Gross Carrying Amount	315	367
Accumulated Amortization	(82)	(59)
Net Carrying Amount	233	308
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	3 years
Gross Carrying Amount	213	219
Accumulated Amortization	(184)	(173)
Net Carrying Amount	29	46
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period (years)	4 years
Gross Carrying Amount	162	166
Accumulated Amortization	(101)	(51)
Net Carrying Amount	$ 61	$ 115

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Remaining amortization period of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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