Short-term and Long-term Borrowings (Details) - USD ($)			6 Months Ended
	Mar. 31, 2023	Mar. 29, 2019	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Cal Water
Debt Instrument [Line Items]
Outstanding borrowings			$ 95,000,000		$ 35,000,000
Parent Company
Debt Instrument [Line Items]
Outstanding borrowings			$ 35,000,000		$ 35,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 600,000,000
Debt instrument, term	5 years
Average borrowing rate			5.78%	1.35%
Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Interest rate		0.00%
Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Interest rate		0.25%
Revolving Credit Facility | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Minimum
Debt Instrument [Line Items]
Interest rate		0.80%
Revolving Credit Facility | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Maximum
Debt Instrument [Line Items]
Interest rate		1.25%
Revolving Credit Facility | Cal Water
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000
Incremental expansion of borrowing capacity	150,000,000
Revolving Credit Facility | Parent Company
Debt Instrument [Line Items]
Maximum borrowing capacity	200,000,000
Incremental expansion of borrowing capacity	$ 50,000,000