Regulatory and Rate Matters - Hazard Sharing Agreement (Details) - Public Service Company of New Mexico [Member] - Tri-State [Member] $ in Millions			12 Months Ended
	Nov. 30, 2016	Jun. 01, 2016 MW	Dec. 31, 2016 USD ($) MWh
Public Utilities, General Disclosures [Line Items]
Hazard sharing agreement		1 year
Agreement to sell the other party capacity and energy (in mw) | MW		100
Number of megawatt hours sold (in mwh) | MWh			482,342
Megawatt hours sold | $			$ 12.8
Number of megawatt hours purchased (in mwh) | MWh			484,632
Megawatt hours purchased | $			$ 12.9
NMPRC [Member]
Public Utilities, General Disclosures [Line Items]
Hazard sharing agreement	5 years		5 years