| **Accumulated Other Comprehensive Income (Tables)**                                      | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
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| **Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]**                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Components of Accumulated Other Comprehensive Income (Loss) [Table Text Block]           | 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 $23 |
| Reclassification out of Accumulated Other Comprehensive Income (Loss) [Table Text Block] | The 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 $— $7                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |

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| - References
No definition available.
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| - Definition
Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss).
+ References
No definition available.
+ Details**Name:**us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
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| - Definition
Tabular disclosure of the components of accumulated other comprehensive income (loss).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580
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