STATEMENTS OF CHANGES IN COMMON SHAREHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Shares	Reinvested Earnings in the Business	GOLDEN STATE WATER COMPANY	GOLDEN STATE WATER COMPANY Common Shares	GOLDEN STATE WATER COMPANY Reinvested Earnings in the Business
Beginning Balance (in shares) at Dec. 31, 2021		36,936,000			170
Beginning balances at Dec. 31, 2021	$ 685,947	$ 258,442	$ 427,505	$ 615,686	$ 356,530	$ 259,156
Add:
Net income	14,162		14,162	8,567		8,567
Issuances of Common Shares under stock-based compensation plans (in shares)		20,000
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)	801	801		742	742
Dividend equivalent rights on stock-based awards not paid in cash	41	$ 41		39	$ 39
Deduct:
Dividends on Common Shares	13,485		13,485	13,500		13,500
Dividend equivalent rights on stock-based awards not paid in cash	41		41	39		39
Ending Balances (in shares) at Mar. 31, 2022		36,956,000			170
Ending balances at Mar. 31, 2022	687,425	$ 259,284	428,141	611,495	$ 357,311	254,184
Beginning Balance (in shares) at Dec. 31, 2021		36,936,000			170
Beginning balances at Dec. 31, 2021	685,947	$ 258,442	427,505	615,686	$ 356,530	259,156
Add:
Net income	$ 59,767			43,380
Issuances of Common Shares under stock-based compensation plans (in shares)	24,612
Ending Balances (in shares) at Sep. 30, 2022		36,961,000			170
Ending balances at Sep. 30, 2022	$ 705,504	$ 260,011	445,493	633,399	$ 357,970	275,429
Beginning Balance (in shares) at Mar. 31, 2022		36,956,000			170
Beginning balances at Mar. 31, 2022	687,425	$ 259,284	428,141	611,495	$ 357,311	254,184
Add:
Net income	19,951		19,951	14,888		14,888
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	338	338		274	274
Dividend equivalent rights on stock-based awards not paid in cash	34	$ 34		31	$ 31
Deduct:
Dividends on Common Shares	13,489		13,489	13,500		13,500
Dividend equivalent rights on stock-based awards not paid in cash	34		34	31		31
Ending Balances (in shares) at Jun. 30, 2022		36,956,000			170
Ending balances at Jun. 30, 2022	694,225	$ 259,656	434,569	613,157	$ 357,616	255,541
Add:
Net income	25,654		25,654	19,925		19,925
Issuances of Common Shares under stock-based compensation plans (in shares)		5,000
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)	315	315		317	317
Dividend equivalent rights on stock-based awards not paid in cash	40	$ 40		37	$ 37
Deduct:
Dividends on Common Shares	14,690		14,690	37		37
Dividend equivalent rights on stock-based awards not paid in cash	40		40
Ending Balances (in shares) at Sep. 30, 2022		36,961,000			170
Ending balances at Sep. 30, 2022	705,504	$ 260,011	445,493	633,399	$ 357,970	275,429
Beginning Balance (in shares) at Dec. 31, 2022		36,962,000			170
Beginning balances at Dec. 31, 2022	709,549	$ 260,158	449,391	643,906	$ 358,123	285,783
Add:
Net income	34,407		34,407	$ 27,463		27,463
Issuances of Common Shares under stock-based compensation plans (in shares)		14,000		1	1
Issuances of Common Shares under stock-based compensation plans	0	$ 0
Issuance of common share to parent				$ 10,000	$ 10,000
Stock-based compensation, net of taxes paid from shares withheld from employees related to net share settlements (Note 4)	1,587	1,587		1,603	1,603
Dividend equivalent rights on stock-based awards not paid in cash	47	$ 47		44	$ 44
Deduct:
Dividends on Common Shares	14,695		14,695	24,700		24,700
Dividend equivalent rights on stock-based awards not paid in cash	47		47	44		44
Ending Balances (in shares) at Mar. 31, 2023		36,976,000			171
Ending balances at Mar. 31, 2023	730,848	$ 261,792	469,056	658,272	$ 369,770	288,502
Beginning Balance (in shares) at Dec. 31, 2022		36,962,000			170
Beginning balances at Dec. 31, 2022	709,549	$ 260,158	449,391	643,906	$ 358,123	285,783
Add:
Net income	$ 104,493			$ 87,589
Issuances of Common Shares under stock-based compensation plans (in shares)	18,351			1
Issuance of common share to parent				$ 10,000
Ending Balances (in shares) at Sep. 30, 2023		36,981,000			171
Ending balances at Sep. 30, 2023	$ 771,337	$ 262,884	508,453	688,525	$ 370,680	317,845
Beginning Balance (in shares) at Mar. 31, 2023		36,976,000			171
Beginning balances at Mar. 31, 2023	730,848	$ 261,792	469,056	658,272	$ 369,770	288,502
Add:
Net income	38,521		38,521	33,533		33,533
Issuances of Common Shares under stock-based compensation plans (in shares)		1,000
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)	396	396		320	320
Dividend equivalent rights on stock-based awards not paid in cash	42	$ 42		39	$ 39
Deduct:
Dividends on Common Shares	14,699		14,699	14,700		14,700
Dividend equivalent rights on stock-based awards not paid in cash	42		42	39		39
Ending Balances (in shares) at Jun. 30, 2023		36,977,000			171
Ending balances at Jun. 30, 2023	755,066	$ 262,230	492,836	677,425	$ 370,129	307,296
Add:
Net income	31,565		31,565	26,593		26,593
Issuances of Common Shares under stock-based compensation plans (in shares)		4,000
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)	606	606		507	507
Dividend equivalent rights on stock-based awards not paid in cash	48	$ 48		44	$ 44
Deduct:
Dividends on Common Shares	15,900		15,900	16,000		16,000
Dividend equivalent rights on stock-based awards not paid in cash	48		48	44		44
Ending Balances (in shares) at Sep. 30, 2023		36,981,000			171
Ending balances at Sep. 30, 2023	$ 771,337	$ 262,884	$ 508,453	$ 688,525	$ 370,680	$ 317,845