| **BUSINESS COMBINIATION - Calculation of Consideration Transferred (Details) $ / shares in Units, $ in Millions** |               | 6 Months Ended | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------|---------------|----------------|-----------------|
||
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| Common shares, outstanding (in shares) | shares                                                                   |          | 218,226,614    | 118,552,599     | 118,280,120 |   |
| Less cash acquired                                                                                                |          | $ (1,130)      | $ 0             | $ 0 | $ 0 |
| L3Harris                                                                                                          |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| L3 shares settled in shares of L3Harris common stock (in shares) | shares                                         | 104,100,000   |           |            |   |   |
| Exchange Ratio                                                                                                    | 1.30          |           |            |   |   |
| Price per share of common stock as of the closing date (in dollars per share) | $ / shares                        | $ 189.13      |           |            |   |   |
| Fair value of Harris common stock issued for Exelis common stock                                                  | $ 19,689      |           |            |   |   |
| Withholding tax liability incurred for converted L3 share-based awards                                            | 45            |           |            |   |   |
| Fair value of replacement award consideration                                                                     | 156           |           |            |   |   |
| Fair value of total consideration                                                                                 | 19,845        |           |            |   |   |
| Less cash acquired                                                                                                | (1,195)       |           |            |   |   |
| Total net consideration transferred                                                                               | 18,650        |           |            |   |   |
| L3Harris | Restricted Stock Units                                                                                 |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| Fair value of Harris common stock issued for Exelis common stock                                                  | 10            |           |            |   |   |
| L3Harris | Stock Options                                                                                          |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| Fair value of Harris common stock issued for Exelis common stock                                                  | $ 101         |           |            |   |   |
| L3Harris | L3                                                                                                     |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| Common shares, outstanding (in shares) | shares                                                                   |          |           | 79,630,000      |   |   |
| L3 shares settled in shares of L3Harris common stock (in shares) | shares                                         | 80,080,000.00 |           |            |   |   |
| L3Harris | L3 | Restricted Stock Units                                                                            |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| L3 shares settled in shares of L3Harris common stock (in shares) | shares                                         | 410,000       |           |            |   |   |
| L3Harris | L3 | Performance Share Units                                                                           |          |           |            |   |   |
| **Business Acquisition [Line Items]**                                                                             |          |           |            |   |   |
| L3 shares settled in shares of L3Harris common stock (in shares) | shares                                         | 40,000.00     |           |            |   |   |

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Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.
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Number of shares of equity interests issued or issuable to acquire entity.
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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.
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Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.
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Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.
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