Commitments and Contingencies - WEG v. OSM NEPA Lawsuit (Details)	12 Months Ended
	Dec. 31, 2019 option	Feb. 28, 2013 state mine lawsuit
Loss Contingencies [Line Items]
Number of options for meeting BTA standards | option	7
Public Service Company of New Mexico | WEG v OSM Lawsuit
Loss Contingencies [Line Items]
Number of mines affected | mine		7
Number of states | state		4
Number of claims filed for relief (in lawsuits)		15
Public Service Company of New Mexico | WEG v OSM Lawsuit | San Juan Generating Station
Loss Contingencies [Line Items]
Number of claims filed for relief (in lawsuits)		2