Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Regulatory Assets and Liabilities
Total Regulatory Assets	$ 298,362	$ 285,692
Total Regulatory Liabilities	186,211	180,428
Future tax benefits due to customers
Regulatory Assets and Liabilities
Total Regulatory Liabilities	134,856	135,027
Retiree group health
Regulatory Assets and Liabilities
Total Regulatory Liabilities	27,294	27,294
HCBA
Regulatory Assets and Liabilities
Total Regulatory Liabilities	13,918	9,687
CEBA
Regulatory Assets and Liabilities
Total Regulatory Liabilities	8,002	7,206
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Total Regulatory Liabilities	230	143
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Total Regulatory Liabilities	1,190	354
Other regulatory liabilities
Regulatory Assets and Liabilities
Total Regulatory Liabilities	721	717
Pension and retiree group health
Regulatory Assets and Liabilities
Total Regulatory Assets	17,114	17,607
Future tax benefits due to customers
Regulatory Assets and Liabilities
Total Regulatory Assets	132,843	130,565
Other accrued benefits
Regulatory Assets and Liabilities
Total Regulatory Assets	24,094	23,280
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Total Regulatory Assets	46,037	29,789
Asset retirement obligations, net
Regulatory Assets and Liabilities
Total Regulatory Assets	24,568	22,935
Interim rates memorandum account (IRMA) long-term accounts receivable
Regulatory Assets and Liabilities
Total Regulatory Assets	$ 7,539	9,032
Tank coating
Regulatory Assets and Liabilities
Recovery Period	10 years
Total Regulatory Assets	$ 16,494	13,680
Recoverable property losses
Regulatory Assets and Liabilities
Total Regulatory Assets	$ 3,313	3,843
PCBA
Regulatory Assets and Liabilities
Recovery Period	1 year
Total Regulatory Assets	$ 19,762	21,500
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Total Regulatory Assets	$ 0	3,342
General district balancing account receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Total Regulatory Assets	$ 365	568
Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Total Regulatory Assets	$ 2,843	5,991
Other regulatory assets
Regulatory Assets and Liabilities
Total Regulatory Assets	$ 3,390	$ 3,560
Minimum | Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Minimum | Interim rates memorandum account (IRMA) long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Maximum | Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	2 years
Maximum | Interim rates memorandum account (IRMA) long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	3 years