Electric Operating Revenues - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) MW	Dec. 31, 2021 USD ($)	May 31, 2022 MW	Jan. 01, 2019	Jan. 01, 2018 MW
Contract with Customers, Asset and Liability [Roll Forward]
Allowance for credit loss	$ (2.3)	$ (1.1)
Other receivables, allowance for credit loss	0.0	1.0
Capitalized contract cost, amortization period				5 years
Contract assets	11.9	0.6
Texas-New Mexico Power Company
Contract with Customers, Asset and Liability [Roll Forward]
Regulatory assets from defaulting REP's	$ 0.8
Public Service Company of New Mexico
Contract with Customers, Asset and Liability [Roll Forward]
Expected exposure to market risk (in megawatts) | MW	65				65
Power to be sold to third party (in megawatts) | MW	36		50		36
Contract with customers, net	$ 151.4	$ 94.9