|**INCOME FROM CONTINUING OPERATIONS PER SHARE (Tables)**                                      | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
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|**Earnings Per Share [Abstract]**                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Income From Continuing Operations Per Share                                                   | The computations of income from continuing operations per common share attributable to L3Harris common shareholders are as follows:Fiscal Years EndedTwo Quarters EndedFiscal Year Ended(In millions, except per share amounts)December 31, 2021January 1, 2021January 3, 2020June 28, 2019Income from continuing operations$1,847$1,121$823$953Adjustments for participating securities outstanding———(2)Income from continuing operations used in per basic and diluted common share calculations (A)$1,847$1,121$823$951Basic weighted average common shares outstanding (B)201.3214.0221.2118.0Impact of dilutive share-based awards1.91.92.52.5Diluted weighted average common shares outstanding (C)203.2215.9223.7120.5Income from continuing operations per basic common share (A)/(B)$9.17$5.24$3.72$8.06Income from continuing operations per diluted common share (A)/(C)$9.09$5.19$3.68$7.89
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|                                                                                              | Fiscal Years Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|(In millions, except per share amounts)                                                       | December 31, 2021                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
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|Income from continuing operations                                                             | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Adjustments for participating securities outstanding                                          | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Income from continuing operations used in per basic and diluted common share calculations (A) | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Basic weighted average common shares outstanding (B)                                          | 201.3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Impact of dilutive share-based awards                                                         | 1.9                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Diluted weighted average common shares outstanding (C)                                        | 203.2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Income from continuing operations per basic common share (A)/(B)                              | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Income from continuing operations per diluted common share (A)/(C)                            | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

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