| **Fair Value Measurements (Tables)**                                    | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| **Fair Value Disclosures [Abstract]**                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |   |
| Fair Value Assets And Liabilities Measured On Recurring Basis           | As of March 31, 2014 and 2013, our assets and liabilities that were measured and recorded at fair value on a recurring basis were as follows (in millions):   Fair Value Measurements at Reporting Date Using   As of March 31, 2014 Quoted Prices inActive Markets for IdenticalFinancial Instruments SignificantOtherObservableInputs SignificantUnobservableInputs   (Level 1) (Level 2) (Level 3) Balance Sheet ClassificationAssets         Money market funds$588 $588 $— $— Cash equivalentsAvailable-for-sale securities:         Corporate bonds279 — 279 — Short-term investmentsCommercial paper146   146   Short-term investments and cash equivalentsU.S. Treasury securities118 118 — — Short-term investments and cash equivalentsU.S. agency securities89 — 89 — Short-term investments and cash equivalentsDeferred compensation plan assets (a)9 9 — — Other assetsTotal assets at fair value$1,229 $715 $514 $—  Liabilities         Contingent consideration (b)$4 $— $— $4 Accrued and other current liabilities and other liabilitiesForeign currency derivatives6 — 6 — Accrued and other current liabilitiesDeferred compensation plan liabilities (a)9 9 — — Other liabilitiesTotal liabilities at fair value$19 $9 $6 $4   |    Fair Value Measurements at Reporting Date Using   As ofMarch 31,2013 Quoted Prices in Active Markets for IdenticalFinancialInstruments SignificantOtherObservableInputs SignificantUnobservableInputs   (Level 1) (Level 2) (Level 3) Balance Sheet ClassificationAssets         Money market funds$469 $469 $— $— Cash equivalentsAvailable-for-sale securities:         Corporate bonds178 — 178 — Short-term investmentsU.S. agency securities91 — 91 — Short-term investments and cash equivalentsU.S. Treasury securities88 88 — — Short-term investments and cash equivalentsCommercial paper73 — 73 — Short-term investments and cash equivalentsDeferred compensation plan assets (a)11 11 — — Other assetsForeign currency derivatives6 — 6 — Other current assetsTotal assets at fair value$916 $568 $348 $—  Liabilities         Contingent consideration (b)$43 $— $— $43 Accrued and other current liabilities and other liabilitiesDeferred compensation plan liabilities (a)12 12 — — Other liabilitiesTotal liabilities at fair value$55 $12 $— $43   |
| Fair Value Measurements Using Significant Unobservable Inputs (Level 3) |    Fair Value Measurements Using Significant Unobservable Inputs (Level 3)         ContingentConsideration  Balance as of March 31, 2013 $43  Change in fair value (c) (35)  Payments (d) (4)  Balance as of March 31, 2014 $4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |    Fair Value Measurements Using Significant Unobservable Inputs (Level 3)         ContingentConsideration  Balance as of March 31, 2012 $112  Change in fair value (c) (64)  Payments (d) (5)  Balance as of March 31, 2013 $43   |
| Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis   |    Fair Value Measurements Using   Net CarryingValue as ofMarch 31, 2014 Quoted Prices inActive Markets for Identical Assets SignificantOther Observable Inputs SignificantUnobservableInputs Total Impairments  for the Fiscal Year Ended March 31, 2014 (Level 1) (Level 2) (Level 3) Assets         Royalty-based asset$— $— $— $— $17Total impairments recorded for non-recurring measurements on assets held as of March 31, 2014       $17                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |    Fair Value Measurements Using   Net CarryingValue as ofMarch 31, 2013 Quoted Prices inActive Markets for Identical Assets SignificantOtherObservableInputs SignificantUnobservableInputs Total Impairments forthe Fiscal Year Ended March 31, 2013 (Level 1) (Level 2) (Level 3) Assets         Acquisition-related intangible assets$4 $— $— $4 $39Total impairments recorded for non-recurring measurements on assets held as of March 31, 2013       $39 |

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| - Definition
Tabular disclosure of assets and liabilities by class, including financial instruments measured at fair value that are classified in shareholders' equity, if any, that are measured at fair value on a nonrecurring basis in periods after initial recognition (for example, impaired assets). Disclosures may include, but are not limited to: (a) the fair value measurements recorded and the reasons for the measurements and (b) the level within the fair value hierarchy in which the fair value measurements are categorized in their entirety (levels 1, 2, 3).
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| - Definition
Tabular disclosure of assets, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).
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| - Definition
Tabular disclosure of the fair value measurement of liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and gains or losses recognized in other comprehensive income (loss) and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs) by class of liability.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19279-110258Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258
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