Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 384,501	$ 257,621
Total Regulatory Liabilities	729,904	683,717
Cost of removal
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	456,471	447,356
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	118,051	118,051
Pension and retiree group health
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	102,255	88,728
Incremental cost balancing account (ICBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	10,795	0
IRMA long-term regulatory liability
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	6,993	0
Health Cost Balancing Account (HCBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	4,291	3,242
PCBA
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	11,220	8,972
Conservation Expense Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	1,324	1,200
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	3,082	2,071
Other components of net periodic benefit cost
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	13,300	10,348
RSF regulatory liability
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	0	2,116
Other regulatory liabilities
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	2,122	1,633
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	158,486	158,486
Other accrued benefits
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	26,975	25,363
Net WRAM and Modified Cost Balancing Account (MCBA) long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	10,490	10,738
Asset retirement obligations, net
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	27,495	26,686
IRMA long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 84,593	3,430
MWRAM
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 31,066	0
Tank coating
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	20,112	19,602
Recoverable property losses
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	2,956	3,121
PCBA
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 4,314	4,182
Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 10,787	2,459
Other regulatory assets
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 7,227	$ 3,554
Minimum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Maximum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	2 years