| **Accumulated Other Comprehensive Income (Tables)**                            | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **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, 2013 are as follows (in millions): Unrealized Gains (Losses) on Available-for-Sale Securities Unrealized Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of September 30, 2013$(4) $(9) $75 $62Other comprehensive loss before reclassifications— (4) (9) (13)Amounts reclassified from accumulated other comprehensive income— 3 — 3Net current-period other comprehensive loss— (1) (9) (10)Balances as of December 31, 2013$(4) $(10) $66 $52 | The changes in accumulated other comprehensive income (loss) by component, net of tax, for the nine months ended December 31, 2013 are as follows (in millions): Unrealized Gains (Losses) on Available-for-Sale Securities Unrealized Gains (Losses) on Derivative Instruments Foreign Currency Translation Adjustments TotalBalances as of March 31, 2013$(4) $— $73 $69Other comprehensive loss before reclassifications— (15) (7) (22)Amounts reclassified from accumulated other comprehensive income— 5 — 5Net current-period other comprehensive loss— (10) (7) (17)Balances as of December 31, 2013$(4) $(10) $66 $52The effects on net loss of amounts reclassified from accumulated other comprehensive income (loss) for the three and nine months ended December 31, 2013 were as follows (in millions):  Amount Reclassified From Accumulated Other Comprehensive Income (loss)  Details about Accumulated Other Comprehensive Income (Loss) Components Three Months Ended December 31, 2013 Nine Months EndedDecember 31, 2013 Statement of Operations ClassificationReclassification adjustment for net realized losses on derivative instruments        $2 $4 Net revenue  1 1 Research and developmentTotal amount reclassified, net of tax $3 $5   |

| X                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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=28358780&loc=SL7669686-108580
+ Details**Name:**us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |