Income Taxes (Gross Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning of period	$ 647us-gaap_UnrecognizedTaxBenefits	$ 560us-gaap_UnrecognizedTaxBenefits	$ 595us-gaap_UnrecognizedTaxBenefits
Additions based on tax positions related to prior years	62	106	46
Reductions based on tax positions related to prior years	(18)	(23)	(106)
Additions based on tax positions related to current year	27	23	31
Reductions based on settlements	(65)	(4)	(2)
Reductions based on the lapse of the applicable statutes of limitations	(12)	(7)	(2)
Unrecognized Tax Benefits, Decrease Resulting from Foreign Currency Translation	(25)	(8)	(2)
Unrecognized tax benefits at end of period	$ 616us-gaap_UnrecognizedTaxBenefits	$ 647us-gaap_UnrecognizedTaxBenefits	$ 560us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

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-Section 50

-Paragraph 15A

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Amount of decrease in unrecognized tax benefits resulting from foreign currency translation.

+ References

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15A

-Subparagraph (a)(1)

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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-Name Accounting Standards Codification

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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-Name Accounting Standards Codification

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