v3.26.1
REVENUE - Narrative (Details) - USD ($)
$ in Thousands
 1 Months Ended 3 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2026
Mar. 31, 2025
Poudre Valley Electric Association        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 34,400  
Poudre Valley Electric Association | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     9.20%  
United Power Inc | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     2.90%  
Salt River Project | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     2.70%  
Core Electric Cooperative | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     4.50%  
UNS Electric, Inc. | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     1.70%  
Utility Member electric sales        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 260,922 $ 256,000
Utility Member electric sales | Poudre Valley Electric Association | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Concentration risk (as a percent)     13.20%  
Non-member electric sales        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 56,790 48,406
Non-member electric sales | United Power Inc | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 10,900  
Concentration risk (as a percent)     19.20%  
Non-member electric sales | Salt River Project | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 10,200  
Concentration risk (as a percent)     17.90%  
Non-member electric sales | Core Electric Cooperative | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 16,900  
Concentration risk (as a percent)     29.80%  
Non-member electric sales | UNS Electric, Inc. | Revenue Benchmark | Customer Concentration Risk        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 6,500  
Concentration risk (as a percent)     11.40%  
Provision for rate refunds - FERC Compliance Filing - Rate Schedule 281        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer $ (5,100) $ (5,100)    
Rate stabilization        
Disaggregation of Revenue [Line Items]        
Revenue from (refunds to) contract with customer     $ 24,840 $ 44,943