Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 359,919	$ 357,406
Total Regulatory Liabilities	845,657	814,551
Cost of removal
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	503,820	483,108
Pension and retiree group health
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	173,964	174,708
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	104,861	106,184
Other components of net periodic benefit cost
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	21,194	18,287
Pension Cost Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	16,048	14,143
PFAS settlement proceeds
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	8,458	0
Incremental Cost Balancing Accounts (ICBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	4,884	6,003
Health Cost Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	4,341	3,630
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	3,089	3,064
Conservation Expense Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	2,889	3,294
Other regulatory liabilities
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	2,109	2,130
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	178,279	178,279
IRMA long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	35,084	46,278
MWRAM long-term regulatory asset
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 31,308	16,353
MWRAM long-term regulatory asset | Minimum
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
MWRAM long-term regulatory asset | Maximum
Regulatory Assets and Liabilities [Line Items]
Recovery Period	2 years
Asset retirement obligations, net
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 30,322	28,883
Other accrued benefits
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	26,702	25,439
Tank coating
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	19,753	21,477
General District Balancing Account receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 9,609	9,393
Customer Assistance Program and Rate Support Fund accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 8,767	9,910
Incremental Cost Balancing Accounts (ICBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	6,708	8,251
Net WRAM and Modified Cost Balancing Account (MCBA) long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	3,657	3,633
Recoverable property losses
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	2,297	2,633
Other regulatory assets
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 7,433	$ 6,877