|**Earnings Per Share (Tables)**                                                                          | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|**Earnings Per Share Reconciliation [Abstract]**                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Computation Of Basic Earnings (Loss) And Diluted Earnings (Loss) Per Share                               | The following table summarizes the computations of basic earnings per share (“Basic EPS”) and diluted earnings per share (“Diluted EPS”). Basic EPS is computed as net income divided by the weighted-average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur from common shares issuable through stock-based compensation plans including stock options, restricted stock, restricted stock units, ESPP purchase rights, warrants, and other convertible securities using the treasury stock method.Three months ended June 30,(In millions, except per share amounts)20172016Net income$644$440Shares used to compute earnings per share:Weighted-average common stock outstanding — basic309301Dilutive potential common shares related to stock award plans and from assumed exercise of stock options44Dilutive potential common shares related to the Convertible Notes(a)—2Dilutive potential common shares related to the Warrants(a)—8Weighted-average common stock outstanding — diluted313315Earnings per share:Basic$2.08$1.46Diluted$2.06$1.40
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|                                                                                                         | Three months ended June 30,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|(In millions, except per share amounts)                                                                  | 2017                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Net income                                                                                               | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Shares used to compute earnings per share:                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Weighted-average common stock outstanding — basic                                                        | 309                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Dilutive potential common shares related to stock award plans and from assumed exercise of stock options | 4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Dilutive potential common shares related to the Convertible Notes(a)                                     | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Dilutive potential common shares related to the Warrants(a)                                              | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted-average common stock outstanding — diluted                                                      | 313                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Earnings per share:                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Basic                                                                                                    | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Diluted                                                                                                  | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

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duration X- DefinitionTabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations.
+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257
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