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Regulatory and Rate Matters Regulatory and Rate Matters (Tables) | 12 Months Ended
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Dec. 31, 2020
Regulated Operations [Abstract] |
Schedule of Rate Increases for Transmission Costs | The following sets forth TNMP’s approved EECRF increases:
Effective Date |  | Aggregate Collection Amount |  | Performance Bonus
|  | (In millions)
March 1, 2018 |  | $ | 6.0 |  |  | $ | 1.1 |
March 1, 2019 |  | 5.6 |  |  | 0.8 |
March 1, 2020 |  | 5.9 |  |  | 0.8 |
The following sets forth TNMP’s recent interim transmission cost rate increases:
Effective Date |  | Approved Increase in Rate Base |  | Annual Increase in Revenue
|  | (In millions)
March 27, 2018 |  | $ | 32 |  |  | $ | 0.6 |
March 21, 2019 |  | 111.8 |  |  | 14.3 |
September 19, 2019 |  | 21.9 |  |  | 3.3 |
March 27, 2020 |  | 59.2 |  |  | 7.8 |
October 7, 2020 |  | 10.8 |  |  | 2.0 |

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