Goodwill and Intangible Assets (Intangible Assets, Net) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	15 years 8 months
Gross Carrying Amount	$ 1,067	$ 1,071
Accumulated Amortization	(483)	(431)
Net Carrying Amount	584us-gaap_FiniteLivedIntangibleAssetsNet	640us-gaap_FiniteLivedIntangibleAssetsNet
Tradenames [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	20 years
Gross Carrying Amount	142	142
Accumulated Amortization	(56)	(49)
Net Carrying Amount	86	93
Technology and Software [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	10 years 8 months
Gross Carrying Amount	357	335
Accumulated Amortization	(149)	(129)
Net Carrying Amount	208	206
Customer-related Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	20 years
Gross Carrying Amount	444	470
Accumulated Amortization	(173)	(160)
Net Carrying Amount	271	310
Favorable Energy Supply Contract [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 6 months
Gross Carrying Amount	124	124
Accumulated Amortization	(105)	(93)
Net Carrying Amount	$ 19	$ 31

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

+ References

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

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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