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Regulatory and Rate Matters - TNMP Schedules (Details) - Texas-New Mexico Power Company - USD ($) $ in Millions							10 Months Ended	12 Months Ended
	Sep. 20, 2021	Mar. 12, 2021	Oct. 07, 2020	Mar. 27, 2020	Sep. 19, 2019	Mar. 21, 2019	Dec. 31, 2021	Feb. 28, 2021	Feb. 29, 2020
Energy efficiency costs
Public Utilities, General Disclosures [Line Items]
Aggregate Collection Amount							$ 5.9	$ 5.9	$ 5.6
Performance Bonus							$ 1.0	$ 0.8	$ 0.8
Transmission Cost of Service Rates
Public Utilities, General Disclosures [Line Items]
Approved Increase in Rate Base	$ 41.2	$ 112.6	$ 10.8	$ 59.2	$ 21.9	$ 111.8
Annual Increase in Revenue	$ 6.3	$ 14.1	$ 2.0	$ 7.8	$ 3.3	$ 14.3

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