Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 340,419	$ 257,621
Total Regulatory Liabilities	734,925	683,717
Cost of removal
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	474,264	447,356
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	109,491	118,051
Pension and retiree group health
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	101,984	88,728
Other components of net periodic benefit cost
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	16,952	10,348
PCBA
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	14,085	8,972
ICBA
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	6,517	0
Health cost balancing account (HCBA)
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	3,979	3,242
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	2,967	2,071
Conservation Expense Balancing Account
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Liabilities	2,828	1,200
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	1,858	1,633
Future tax benefits due to customers
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	158,486	158,486
IRMA long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	49,505	3,430
Asset retirement obligations, net
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	29,134	26,686
Other accrued benefits
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	26,663	25,363
Tank coating
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	21,345	19,602
MWRAM
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 14,253	0
MWRAM | Minimum
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
MWRAM | Maximum
Regulatory Assets and Liabilities [Line Items]
Recovery Period	2 years
General district balancing account
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 10,945	390
Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 9,056	2,459
ICBA
Regulatory Assets and Liabilities [Line Items]
Recovery Period	1 year
Total Regulatory Assets	$ 9,479	0
Net WRAM and modified cost balancing account (MCBA) long-term accounts receivable
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	4,216	10,738
PCBA
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	0	4,182
Recoverable property losses
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	2,625	3,121
Other regulatory assets
Regulatory Assets and Liabilities [Line Items]
Total Regulatory Assets	$ 4,712	$ 3,164