Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Regulatory Assets and Liabilities
Regulatory Assets	$ 339,865	$ 357,406
Regulatory Liabilities	929,814	814,551
Cost of removal
Regulatory Assets and Liabilities
Regulatory Liabilities	523,813	483,108
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory Liabilities	219,133	174,708
Future tax benefits due to customers
Regulatory Assets and Liabilities
Regulatory Liabilities	103,662	106,184
PFAS settlement proceeds
Regulatory Assets and Liabilities
Regulatory Liabilities	25,193	0
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Regulatory Liabilities	24,248	18,287
Pension Cost Balancing Account (PCBA)
Regulatory Assets and Liabilities
Regulatory Liabilities	17,837	14,143
Conservation Expense Balancing Account (CEBA)
Regulatory Assets and Liabilities
Regulatory Liabilities	5,202	3,294
Health Cost Balancing Account (HCBA)
Regulatory Assets and Liabilities
Regulatory Liabilities	4,149	3,630
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Regulatory Liabilities	3,117	3,064
ICBA
Regulatory Assets and Liabilities
Regulatory Liabilities	2,144	6,003
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory Liabilities	1,316	2,130
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory Assets	199,465	178,279
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory Assets	30,073	28,883
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory Assets	26,263	25,439
IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	22,077	46,278
Tank coating
Regulatory Assets and Liabilities
Regulatory Assets	19,495	21,477
MWRAM long-term regulatory asset
Regulatory Assets and Liabilities
Regulatory Assets	$ 12,876	16,353
MWRAM long-term regulatory asset | Minimum
Regulatory Assets and Liabilities
Recovery Period	1 year
MWRAM long-term regulatory asset | Maximum
Regulatory Assets and Liabilities
Recovery Period	2 years
General district balancing account receivable
Regulatory Assets and Liabilities
Regulatory Assets	$ 9,844	9,393
ICBA
Regulatory Assets and Liabilities
Recovery Period	1 year
Regulatory Assets	$ 4,722	8,251
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	$ 4,078	3,633
Customer Assistance Program (CAP) and Rate Support Fund (RSF) accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Regulatory Assets	$ 2,651	9,910
Recoverable property losses
Regulatory Assets and Liabilities
Regulatory Assets	2,051	2,633
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory Assets	$ 6,270	$ 6,877