| **Accumulated Other Comprehensive Income**                               | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| 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 September 30, 2016 and 2015 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 June 30, 2016$3 $36 $(36) $3Other comprehensive income (loss) before reclassifications(1) (1) (6) (8)Amounts reclassified from accumulated other comprehensive income (loss)(1) (4) — (5)Total other comprehensive income (loss), net of tax(2) (5) (6) (13)Balance as of September 30, 2016$1 $31 $(42) $(10) Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of June 30, 2015$(4) $5 $(15) $(14)Other comprehensive income (loss) before reclassifications2 5 (32) (25)Amounts reclassified from accumulated other comprehensive income (loss)(1) (4) — (5)Total other comprehensive income (loss), net of tax1 1 (32) (30)Balance as of September 30, 2015$(3) $6 $(47) $(44)The changes in accumulated other comprehensive income (loss) by component, net of tax, for the six months ended September 30, 2016 and 2015 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, 2016$1 $14 $(31) $(16)Other comprehensive income (loss) before reclassifications1 27 (11) 17Amounts reclassified from accumulated other comprehensive income (loss)(1) (10) — (11)Total other comprehensive income (loss), net of tax— 17 (11) 6Balance as of September 30, 2016$1 $31 $(42) $(10) Unrealized Net Gains (Losses) on Available-for-Sale Securities Unrealized Net Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of March 31, 2015$(3) $21 $(16) $2Other comprehensive income (loss) before reclassifications1 (8) (31) (38)Amounts reclassified from accumulated other comprehensive income (loss)(1) (7) — (8)Total other comprehensive income (loss), net of tax— (15) (31) (46)Balance as of September 30, 2015$(3) $6 $(47) $(44)The effects on net income of amounts reclassified from accumulated other comprehensive income (loss) for the three and six months ended September 30, 2016 were as follows (in millions): Amount Reclassified From Accumulated Other Comprehensive Income (Loss)Statement of Operations ClassificationThree Months Ended September 30, 2016Six Months Ended September 30, 2016(Gains) losses on available-for-sale securitiesInterest and other income (expense), net $(1) $(1)Net of tax$(1)$(1)(Gains) losses on cash flow hedges from forward contracts    Net revenue$(4)$(9)Research and development—(1)Net of tax $(4) $(10)     Total (gain) loss reclassified, net of tax$(5)$(11)The effects on net income of amounts reclassified from accumulated other comprehensive income (loss) for the three and six months ended September 30, 2015 were as follows (in millions):  Amount Reclassified From Accumulated Other Comprehensive Income (Loss)Statement of Operations Classification Three Months Ended September 30, 2015 Six Months Ended September 30, 2015(Gains) losses on available-for-sale securities    Interest and other income (expense), net $(1) $(1)Net of tax $(1) $(1)     (Gains) losses on cash flow hedges from forward contracts    Net revenue $(6) $(14)Research and development 2 7Net of tax $(4) $(7)     Total (gain) loss reclassified, net of tax $(5) $(8) |

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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 |