| **Accumulated Other Comprehensive Income**                               | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              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| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        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| Comprehensive Income (Loss)                                              | (5) ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)The changes in accumulated other comprehensive income (loss) by component, net of tax, for the three months ended December 31, 2015 and 2014 are as follows (in millions): Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of September 30, 2015$(3) $6 $(47) $(44)Other comprehensive income (loss) before reclassifications(4) 10 (16) (10)Amounts reclassified from accumulated other comprehensive income (loss)1 (4) — (3)Total other comprehensive income (loss), net of tax(3) 6 (16) (13)Balance as of December 31, 2015$(6) $12 $(63) $(57) Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of September 30, 2014$(4) $7 $50 $53Other comprehensive income (loss) before reclassifications(1) 1 (30) (30)Amounts reclassified from accumulated other comprehensive income (loss)(1) 1 — —Total other comprehensive income (loss), net of tax(2) 2 (30) (30)Balance as of December 31, 2014$(6) $9 $20 $23The changes in accumulated other comprehensive income (loss) by component, net of tax, for the nine months ended December 31, 2015 and 2014 are as follows (in millions): Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of March 31, 2015$(3) $21 $(16) $2Other comprehensive income (loss) before reclassifications(3) 2 (47) (48)Amounts reclassified from accumulated other comprehensive income (loss)— (11) — (11)Total other comprehensive income (loss), net of tax(3) (9) (47) (59)Balance as of December 31, 2015$(6) $12 $(63) $(57) Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of March 31, 2014$(4) $(10) $51 $37Other comprehensive income (loss) before reclassifications(1) 11 (31) (21)Amounts reclassified from accumulated other comprehensive income (loss)(1) 8 — 7Total other comprehensive income (loss), net of tax(2) 19 (31) (14)Balance as of December 31, 2014$(6) $9 $20 $23The effects on net income of amounts reclassified from accumulated other comprehensive income (loss) for the three and nine months ended December 31, 2015 were as follows (in millions): Amount Reclassified From Accumulated Other Comprehensive Income (Loss)Statement of Operations ClassificationThree Months Ended December 31, 2015Nine Months Ended December 31, 2015Gains and losses on available-for-sale securitiesInterest and other income (expense), net $1 $—Net of tax$1$—Gains and losses on cash flow hedges from forward contracts    Net revenue$(5)$(19)Research and development18Net of tax $(4) $(11)     Total amount reclassified, net of tax$(3)$(11)The net impact from our available-for-sale securities and cash flow hedging activities in our Condensed Consolidated Statements of Operations for the three and nine months ended December 31, 2015 was a gain of $3 million and $11 million, respectively.The effects on net income of amounts reclassified from accumulated other comprehensive income (loss) for the three and nine months ended December 31, 2014 were as follows (in millions):  Amount Reclassified From Accumulated Other Comprehensive Income (Loss)Statement of Operations Classification Three Months Ended December 31, 2014 Nine Months Ended December 31, 2014Gains and losses on available-for-sale securities    Interest and other income (expense), net $(1) $(1)Net of tax $(1) $(1)     Gains and losses on cash flow hedges from forward contracts    Net revenue $(2) $3Research and development 3 5Net of tax $1 $8     Total amount reclassified, net of tax $— $7The net impact from our available-for-sale and cash flow hedging activities in our Condensed Consolidated Statements of Operations for the nine months ended December 31, 2014 was a loss of $7 million. The net impact from our available-for-sale and cash flow hedging activities in our Condensed Consolidated Statements of Operations for the three months ended December 31, 2014 was immaterial. |

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| - References
No definition available.
+ Details**Name:**us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
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| - Definition
Tabular disclosure of condensed statement of comprehensive income (loss) including, but not limited to, statements of comprehensive income (loss) of consolidated entities and consolidation eliminations.
+ References
No definition available.
+ Details**Name:**us-gaap_CondensedStatementOfComprehensiveIncomeTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |