Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 367,231	$ 357,406
Total Regulatory Liabilities	826,595	814,551
Cost of removal
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	493,688	483,108
Pension and retiree group health
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	174,341	174,708
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	105,402	106,184
Other components of net periodic benefit cost
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	19,645	18,287
Pension Cost Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	15,091	14,143
Incremental Cost Balancing Accounts (ICBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	5,700	6,003
Health Cost Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	4,458	3,630
Conservation Expense Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	3,199	3,294
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	3,075	3,064
Other regulatory liabilities
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	1,996	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	41,690	46,278
Asset retirement obligations, net
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	29,599	28,883
MWRAM long-term regulatory asset
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 28,750	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
Other accrued benefits
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 26,671	25,439
Tank coating
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 20,822	21,477
Customer Assistance Program and Rate Support Fund accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 10,529	9,910
General District Balancing Account receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	9,499	9,393
Incremental Cost Balancing Accounts (ICBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	8,023	8,251
Net WRAM and Modified Cost Balancing Account (MCBA) long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	3,460	3,633
Recoverable property losses
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	2,463	2,633
Other regulatory assets
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 7,446	$ 6,877