CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 127,848	$ 190,085	$ 51,376
Other comprehensive income (loss):
Unrecoverable defined pension benefit plan costs, net of taxes of $0, $3,823, and $0, respectively	0	(9,840)	0
Amortization of defined benefit pension plans, net of taxes of $286, $456, and $0, respectively	737	1,175	0
Unrealized actuarial (loss) gain, net of taxes of $(2,891), $563, and $0, respectively	(7,442)	1,448	0
Other comprehensive loss, net of tax	(6,705)	(7,217)	0
Comprehensive income	121,143	182,868	51,376
Comprehensive loss attributable to noncontrolling interest	(363)	(722)	(535)
Comprehensive income attributable to California Water Service Group	$ 121,506	$ 183,590	$ 51,911