XML 135 R105.htm IDEA: XBRL DOCUMENT v3.20.4
Commitments and Contingencies - Coal Supply (Details) - USD ($)
 1 Months Ended 12 Months Ended
Dec. 31, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jan. 31, 2016
Other Commitments [Line Items]            
Other current assets $ 64,549,000 $ 64,549,000 $ 44,472,000      
Four Corners | Coal Supply            
Other Commitments [Line Items]            
Payments for relief from obligations   75,000,000        
Public Service Company of New Mexico            
Other Commitments [Line Items]            
Other current assets 51,908,000 51,908,000 36,561,000      
Public Service Company of New Mexico | Loss on long-term purchase commitment | San Juan Generating Station            
Other Commitments [Line Items]            
Annual funding post-term reclamation trust   3,200,000 5,500,000 $ 10,000,000.0    
Public Service Company of New Mexico | Increase in coal mine decommissioning liability            
Other Commitments [Line Items]            
Net expense     800,000      
Public Service Company of New Mexico | Increase in coal mine decommissioning liability | Loss on long-term purchase commitment            
Other Commitments [Line Items]            
Estimated underpaid surface mining royalties under proposed rate change         $ 2,500,000  
Public Service Company of New Mexico | Mine Reclamation Trust | San Juan Generating Station            
Other Commitments [Line Items]            
Reclamation trust funding, next fiscal year 5,800,000 5,800,000        
Reclamation trust funding, year 2 6,200,000 6,200,000        
Reclamation trust funding, year 3 0 0        
Public Service Company of New Mexico | Mine Reclamation Trust | Four Corners            
Other Commitments [Line Items]            
Funds contributed to mine reclamation trust   2,000,000.0 2,300,000 2,300,000    
Funds contributed next fiscal year through year five 2,100,000 2,100,000        
Public Service Company of New Mexico | Underground and Surface | Increase in coal mine decommissioning liability            
Other Commitments [Line Items]            
Net expense       39,200,000    
Public Service Company of New Mexico | Surface | Loss on long-term purchase commitment            
Other Commitments [Line Items]            
Liability for interim storage costs 71,700,000 71,700,000 70,300,000      
Public Service Company of New Mexico | Surface | Increase in coal mine decommissioning liability            
Other Commitments [Line Items]            
Net expense 3,600,000     29,800,000    
Public Service Company of New Mexico | Underground | Loss on long-term purchase commitment            
Other Commitments [Line Items]            
Liability for interim storage costs 26,100,000 26,100,000 25,300,000      
Public Service Company of New Mexico | Underground | Increase in coal mine decommissioning liability            
Other Commitments [Line Items]            
Net expense 100,000   9,300,000 $ 9,400,000    
Public Service Company of New Mexico | San Juan Generating Station | Surface | Loss on long-term purchase commitment            
Other Commitments [Line Items]            
Estimate of possible loss 80,100,000 80,100,000        
Public Service Company of New Mexico | San Juan Generating Station | Underground | Loss on long-term purchase commitment            
Other Commitments [Line Items]            
Estimate of possible loss 35,100,000 35,100,000        
Public Service Company of New Mexico | San Juan Generating Station | Coal Supply            
Other Commitments [Line Items]            
Other current assets 26,300,000 26,300,000 $ 26,300,000      
Public Service Company of New Mexico | Four Corners | Increase in coal mine decommissioning liability            
Other Commitments [Line Items]            
Net expense   2,500,000        
Public Service Company of New Mexico | San Juan Generating Station And Four Corners | Surface            
Other Commitments [Line Items]            
Capacity to be collected for final reclamation   100,000,000        
NM Capital | San Juan Generating Station | Coal Supply            
Other Commitments [Line Items]            
Coal mine reclamation bonds to be posted with NMMMD 118,700,000 118,700,000        
Issuance in letters of credit $ 30,300,000 $ 30,300,000       $ 30,300,000