Taxes on Income - Current and Deferred Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Current
Federal	$ 25,177	$ 19,680	$ 26,327
State	10,579	8,451	10,489
Total current tax expense	35,756	28,131	36,816
Deferred
Federal	4,696	1,656	4,157
State	(1,096)	386	626
Total deferred tax (benefit) expense	3,600	2,042	4,783
Total income tax expense operations	$ 39,356	$ 30,173	$ 41,599
Tax at U.S. federal statutory tax rate (amount)	21.00%	21.00%	21.00%
State income tax, net of federal benefit, amount	4.50%	4.40%	5.90%
Effective income tax rate	(23.20%)	(20.20%)	(25.00%)
Nontaxable or nondeductible items	0.30%	0.30%	0.30%
California
Deferred
State income tax, net of federal benefit, amount	50.00%	50.00%	50.00%
GSWC
Current
Federal	$ 20,287	$ 13,570	$ 22,564
State	9,334	6,551	10,176
Total current tax expense	29,621	20,121	32,740
Deferred
Federal	2,442	1,362	2,867
State	(513)	1,386	82
Total deferred tax (benefit) expense	1,929	2,748	2,949
Total income tax expense operations	$ 31,550	$ 22,869	$ 35,689
Tax at U.S. federal statutory tax rate (amount)	21.00%	21.00%	21.00%
State income tax, net of federal benefit, amount	5.40%	4.90%	6.60%
Effective income tax rate	(23.80%)	(19.50%)	(25.80%)
Nontaxable or nondeductible items	0.50%	0.50%	0.40%
GSWC | California
Deferred
State income tax, net of federal benefit, amount	100.00%	100.00%	100.00%