STATEMENTS OF CHANGES IN COMMON SHAREHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Stock Including Additional Paid in Capital	Retained Earnings	GOLDEN STATE WATER COMPANY	GOLDEN STATE WATER COMPANY Common Stock Including Additional Paid in Capital	GOLDEN STATE WATER COMPANY Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2024		38,151,000			173.7586
Beginning balances at Dec. 31, 2024	$ 920,051	$ 355,143	$ 564,908	$ 805,833	$ 413,797	$ 392,036
Add:
Net income	26,844		26,844	19,906		19,906
Issuance of Common Shares from an at-the-market program, net of issuance costs (in shares)		335,000
Issuance of Common Shares from an at-the-market program, net of issuance costs	25,648	$ 25,648
Issuances of Common Shares under stock-based compensation plans (in shares)		23,000
Issuances of Common Shares under stock-based compensation plans	0	$ 0
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	1,626	1,626		1,634	1,634
Dividend equivalent rights on stock-based awards not paid in cash	63	$ 63		57	$ 57
Deduct:
Dividends on Common Shares	17,762		17,762
Dividend equivalent rights on stock-based awards not paid in cash	63		63	57		57
Ending Balances (in shares) at Mar. 31, 2025		38,509,000			173.7586
Ending balances at Mar. 31, 2025	956,407	$ 382,480	573,927	827,373	$ 415,488	411,885
Beginning Balance (in shares) at Dec. 31, 2024		38,151,000			173.7586
Beginning balances at Dec. 31, 2024	920,051	$ 355,143	564,908	805,833	$ 413,797	392,036
Add:
Net income	$ 60,534			48,046
Issuances of Common Shares under stock-based compensation plans (in shares)	23,463
Ending Balances (in shares) at Jun. 30, 2025		38,509,000			177.4086
Ending balances at Jun. 30, 2025	$ 972,519	$ 382,900	589,619	887,836	$ 465,875	421,961
Beginning Balance (in shares) at Mar. 31, 2025		38,509,000			173.7586
Beginning balances at Mar. 31, 2025	956,407	$ 382,480	573,927	827,373	$ 415,488	411,885
Add:
Net income	33,690		33,690	28,140		28,140
Issuance costs from an at-the-market offering program	(78)	(78)
Issuance of Common Shares from an at-the-market program, net of issuance costs (in shares)					3.6500
Issuance of Common Shares from an at-the-market program, net of issuance costs				50,005	$ 50,005
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	426	426		318	318
Dividend equivalent rights on stock-based awards not paid in cash	72	$ 72		64	$ 64
Deduct:
Dividends on Common Shares	17,926		17,926	18,000		18,000
Dividend equivalent rights on stock-based awards not paid in cash	72		72	64		64
Ending Balances (in shares) at Jun. 30, 2025		38,509,000			177.4086
Ending balances at Jun. 30, 2025	972,519	$ 382,900	589,619	887,836	$ 465,875	421,961
Beginning Balance (in shares) at Dec. 31, 2025		39,082,000			178.3836
Beginning balances at Dec. 31, 2025	1,045,581	$ 425,153	620,428	933,737	$ 478,494	455,243
Add:
Net income	29,948		29,948	21,683		21,683
Issuance of Common Shares from an at-the-market program, net of issuance costs (in shares)		84,000
Issuance of Common Shares from an at-the-market program, net of issuance costs	6,185	$ 6,185
Issuances of Common Shares under stock-based compensation plans (in shares)		26,000
Issuances of Common Shares under stock-based compensation plans	0	$ 0
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	1,830	1,830		1,873	1,873
Dividend equivalent rights on stock-based awards not paid in cash	70	$ 70		63	$ 63
Deduct:
Dividends on Common Shares	19,699		19,699	19,700		19,700
Dividend equivalent rights on stock-based awards not paid in cash	70		70	63		63
Ending Balances (in shares) at Mar. 31, 2026		39,192,000			178.3836
Ending balances at Mar. 31, 2026	1,063,845	$ 433,238	630,607	937,593	$ 480,430	457,163
Beginning Balance (in shares) at Dec. 31, 2025		39,082,000			178.3836
Beginning balances at Dec. 31, 2025	1,045,581	$ 425,153	620,428	933,737	$ 478,494	455,243
Add:
Net income	$ 73,222			57,784
Issuances of Common Shares under stock-based compensation plans (in shares)	26,023
Ending Balances (in shares) at Jun. 30, 2026		39,635,000			178.3836
Ending balances at Jun. 30, 2026	$ 1,121,480	$ 467,473	654,007	962,189	$ 480,797	481,392
Beginning Balance (in shares) at Mar. 31, 2026		39,192,000			178.3836
Beginning balances at Mar. 31, 2026	1,063,845	$ 433,238	630,607	937,593	$ 480,430	457,163
Add:
Net income	43,274		43,274	36,101		36,101
Issuance of Common Shares from an at-the-market program, net of issuance costs (in shares)		443,000
Issuance of Common Shares from an at-the-market program, net of issuance costs	33,750	$ 33,750
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	406	406		295	295
Dividend equivalent rights on stock-based awards not paid in cash	79	$ 79		72	$ 72
Deduct:
Dividends on Common Shares	19,795		19,795	11,800		11,800
Dividend equivalent rights on stock-based awards not paid in cash	79		79	72		72
Ending Balances (in shares) at Jun. 30, 2026		39,635,000			178.3836
Ending balances at Jun. 30, 2026	$ 1,121,480	$ 467,473	$ 654,007	$ 962,189	$ 480,797	$ 481,392