Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2018	Dec. 31, 2017
Schedule of Goodwill and Other Intangible Assets [Line Items]
Goodwill	$ 278,297	$ 278,297		$ 278,297
Public Service Company of New Mexico
Schedule of Goodwill and Other Intangible Assets [Line Items]
Goodwill	51,632	51,632	$ 51,600
Percentage of fair value in excess of carrying amount			19.00%
Texas-New Mexico Power Company
Schedule of Goodwill and Other Intangible Assets [Line Items]
Goodwill	$ 226,665	$ 226,665	$ 226,700
Percentage of fair value in excess of carrying amount			32.00%