Regulatory and Rate Matters - TNMP (Details) - Texas-New Mexico Power Company $ in Millions	May 29, 2026 USD ($)	Nov. 14, 2025 USD ($)	Sep. 30, 2026 USD ($)	Jun. 25, 2026 USD ($)	Oct. 15, 2025 USD ($)	Sep. 22, 2025 USD ($)	Mar. 12, 2025 USD ($)
Public Utilities, General Disclosures [Line Items]
Requested recovery rate	$ 2,800.0	$ 2,800.0
Requested on ROE, percent	0.0965	0.104
Equity ratio, percent	0.45	0.4754
Restoration costs		5 years
Sales and use tax refund					$ 5.1		$ 34.6
Consultant fees				$ 1.1		$ 7.5
Capital projects				3.8		24.7
Offset related interest expense				$ 0.2		2.1
Other related expenses						$ 0.3
Balance Sheet Location [Axis]: us-gaap:DeferredCreditsAndOtherLiabilitiesNoncurrent
Public Utilities, General Disclosures [Line Items]
Large load interconnection, deposits			$ 52.7
Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent
Public Utilities, General Disclosures [Line Items]
Large load interconnection, deposits			$ 51.8
Hurricane
Public Utilities, General Disclosures [Line Items]
Requested recovery rate		$ 20.5