v3.26.1
Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 334,709 $ 339,865
Total Regulatory Liabilities 903,905 929,814
Cost of removal    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 537,504 523,813
Pension and retiree group health    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 217,692 219,133
Future tax benefits due to customers    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 102,508 103,662
Other components of net periodic benefit cost    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 28,214 24,248
Incremental Cost Balancing Accounts (ICBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 4,257 2,144
PFAS settlement proceeds    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 4,293 25,193
Pension Cost Balancing Account (PCBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 1,247 17,837
Conservation Expense Balancing Account (CEBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 3,153 5,202
Net WRAM and MCBA long-term payable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 0 3,117
Health Cost Balancing Account (HCBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 1,835 4,149
Other regulatory liabilities    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 3,202 1,316
Property-related temporary differences (tax benefits flowed through to customers)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 199,465 199,465
M-WRAM long-term regulatory asset    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 24,152 12,876
M-WRAM long-term regulatory asset | Minimum    
Regulatory Assets and Liabilities [Line Items]    
Recovery Period 1 year  
M-WRAM long-term regulatory asset | Maximum    
Regulatory Assets and Liabilities [Line Items]    
Recovery Period 2 years  
IRMA long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 21,216 22,077
Other accrued benefits    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 28,398 26,263
Asset retirement obligations, net    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 31,577 30,073
Tank coating    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 18,584 19,495
General District Balancing Account (GDBA) long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 588 9,844
Customer Assistance Program and Rate Support Fund accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Recovery Period 1 year  
Total Regulatory Assets $ 254 2,651
Net WRAM and Modified Cost Balancing Account (MCBA) long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 0 4,078
Incremental Cost Balancing Accounts (ICBA)    
Regulatory Assets and Liabilities [Line Items]    
Recovery Period 1 year  
Total Regulatory Assets $ 3,646 4,722
Recoverable property losses    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 1,765 2,051
Other regulatory assets    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 5,064 $ 6,270