v3.26.3
Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 320,115 $ 339,865
Total Regulatory Liabilities 920,323 929,814
Cost of removal    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 548,503 523,813
Pension and retiree group health    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 216,972 219,133
Future tax benefits due to customers    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 101,930 103,662
Other components of net periodic benefit cost    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 30,180 24,248
Conservation Expense Balancing Account (CEBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 5,929 5,202
Customer Assistance Program and Rate Support Fund accounts payable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 4,237 0
PFAS settlement proceeds    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 3,397 25,193
General District Balancing Account (GDBA) long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 3,129 2,144
Health Cost Balancing Account (HCBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 2,497 4,149
Pension Cost Balancing Account (PCBA)    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 1,933 17,837
Net WRAM and MCBA long-term payable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 0 3,117
Other regulatory liabilities    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Liabilities 1,616 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
Asset retirement obligations, net    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 32,340 30,073
Other accrued benefits    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 28,406 26,263
Tank coating    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 17,753 19,495
M-WRAM long-term regulatory asset    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 13,307 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 $ 11,165 22,077
General District Balancing Account (GDBA) long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Recovery Period 1 year  
Total Regulatory Assets $ 8,507 4,722
Recoverable property losses    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 1,609 2,051
General District Balancing Account (GDBA) long-term accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 744 9,844
Customer Assistance Program and Rate Support Fund accounts receivable    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets 0 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
Other regulatory assets    
Regulatory Assets and Liabilities [Line Items]    
Total Regulatory Assets $ 6,819 $ 6,270