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Regulatory and Rate Matters - TNMP Narrative (Details) - Texas-New Mexico Power Company [Member] - Advanced Meter System Deployment and Surcharge Request [Member] | 1 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jul. 30, 2011 USD ($) | Mar. 31, 2016 USD ($) | Apr. 22, 2016 customer | Oct. 02, 2015 USD ($) | Aug. 15, 2013 USD ($) customer
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Approved deployment costs | $ 113,400,000 |  |  |  |
Collection of deployment costs through surcharge period | 12 years |  |  |  |
Completion period of advanced meter deployment | 5 years |  |  |  |
Recovery in cost through initial fees |  |  |  |  | $ 200,000
Ongoing annual expenses |  |  |  |  | 500,000
Approved non-standard metering ongoing expenses monthly charge |  |  |  |  | $ 36.78
Presumed number of customers that will elect non-standard meter service (in customers) | customer |  |  |  |  | 1,081
Cost and savings reconciliation filed with regulators, capital cost savings |  |  |  | $ 71,000,000 |
Cost and savings reconciliation filed with regulators, operations and maintenance savings |  |  |  | $ 18,000,000 |
Program costs incurred to date |  | $ 1,500,000 |  |  |
Subsequent Event [Member] |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Current number of customers that have elected non-standard meter service (in customers) | customer |  |  | 98 |  |
Minimum [Member] |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Approved non-standard metering service cost, initial fee range |  |  |  |  | $ 63.97
Maximum [Member] |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Approved non-standard metering service cost, initial fee range |  |  |  |  | $ 168.61

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