XML 140 R115.htm IDEA: XBRL DOCUMENT v3.10.0.1
Regulatory and Rate Matters - Hazard Sharing Agreement (Details) - Public Service Company of New Mexico - Tri-State
GWh in Millions, $ in Millions
 12 Months Ended
Jun. 01, 2017
Jun. 01, 2016
MW
Dec. 31, 2018
USD ($)
GWh
Dec. 31, 2017
USD ($)
GWh
Dec. 31, 2016
USD ($)
GWh
Public Utilities, General Disclosures [Line Items]          
Hazard sharing agreement 5 years 1 year      
Agreement to sell the other party capacity and energy (in mw) | MW   100      
Number of hours sold (in GWh) | GWh     725.7 827.1 482.3
Hours sold (in dollars) | $     $ 25.8 $ 23.6 $ 12.8
Number of hours purchased (in GWh) | GWh     822.7 849.0 484.6
Hours purchased (in dollars) | $     $ 28.7 $ 24.2 $ 12.9