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Long-Term Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Feb. 06, 2023
Debt Instrument [Line Items]
Total debt	$ 1,719,824	$ 1,583,441
Unamortized debt premium and discount, net	(56)	1,583
Unamortized debt issuance costs	(9,216)	(9,350)
Current portion	(3,648)	(48,975)
Total long-term debt, less current portion	1,706,904	1,526,699
SJW Group
Debt Instrument [Line Items]
Total long-term debt, less current portion	557,430	557,028
SJW Group \| Senior notes
Debt Instrument [Line Items]
Total debt	$ 560,000	560,000
SJW Group \| Senior notes \| Minimum
Debt Instrument [Line Items]
Rate	2.47%
SJW Group \| Senior notes \| Maximum
Debt Instrument [Line Items]
Rate	3.53%
SJWC \| California Pollution Control Financing Authority Revenue Bond
Debt Instrument [Line Items]
Total debt	$ 575,000	540,000
SJWC \| Senior notes
Debt Instrument [Line Items]
Total debt	$ 505,000	470,000
SJWC \| Senior notes \| Minimum
Debt Instrument [Line Items]
Rate	3.00%
SJWC \| Senior notes \| Maximum
Debt Instrument [Line Items]
Rate	7.20%
SJWC \| Public Utility, Bonds \| California Pollution Control Financing Authority Revenue Bond
Debt Instrument [Line Items]
Total debt	$ 70,000	70,000
SJWC \| Public Utility, Bonds \| California Pollution Control Financing Authority Revenue Bond \| Minimum
Debt Instrument [Line Items]
Rate	4.75%
SJWC \| Public Utility, Bonds \| California Pollution Control Financing Authority Revenue Bond \| Maximum
Debt Instrument [Line Items]
Rate	4.75%
CTWS \| Bank term loans
Debt Instrument [Line Items]
Rate			4.09%
Total debt	$ 14,389	16,457
CTWS \| Bank term loans \| Minimum
Debt Instrument [Line Items]
Rate	4.09%
CTWS \| Bank term loans \| Maximum
Debt Instrument [Line Items]
Rate	4.15%
CWC
Debt Instrument [Line Items]
Total debt	$ 388,672	313,345
CWC \| Senior notes
Debt Instrument [Line Items]
Total debt	$ 270,000	195,000
CWC \| Senior notes \| Minimum
Debt Instrument [Line Items]
Rate	3.07%
CWC \| Senior notes \| Maximum
Debt Instrument [Line Items]
Rate	6.46%
CWC \| Public Utility, Bonds \| Connecticut Innovations Revenue Bonds, variable rate
Debt Instrument [Line Items]
Total debt	$ 22,050	22,050
CWC \| Bank term loans
Debt Instrument [Line Items]
Total debt	$ 96,295	96,295
CWC \| Bank term loans \| Minimum
Debt Instrument [Line Items]
Rate	4.04%
CWC \| Bank term loans \| Maximum
Debt Instrument [Line Items]
Rate	4.75%
CWC \| Revolving Fund Loan \| State revolving fund loans
Debt Instrument [Line Items]
Rate	2.00%
Total debt	$ 327	0
TWC
Debt Instrument [Line Items]
Total debt	109,000	60,000
TWC \| Senior notes
Debt Instrument [Line Items]
Total debt	$ 15,000	15,000
TWC \| Senior notes \| Minimum
Debt Instrument [Line Items]
Rate	6.27%
TWC \| Senior notes \| Maximum
Debt Instrument [Line Items]
Rate	6.27%
TWC \| Bank term loans
Debt Instrument [Line Items]
Total debt	$ 65,000	45,000
TWC \| Bank term loans \| Minimum
Debt Instrument [Line Items]
Rate	4.01%
TWC \| Bank term loans \| Maximum
Debt Instrument [Line Items]
Rate	6.47%
TWC \| Seller financing debt
Debt Instrument [Line Items]
Total debt	$ 29,000	0
Interest rate effective percentage	5.61%
TWR \| Seller financing debt
Debt Instrument [Line Items]
Total debt	$ 0	29,000
Interest rate effective percentage	5.61%
MWC
Debt Instrument [Line Items]
Total debt	$ 72,763	64,639
MWC \| Public Utility, Bonds \| Other First Mortgage Bond
Debt Instrument [Line Items]
Rate	8.95%
Total debt	$ 0	900
MWC \| Bank term loans
Debt Instrument [Line Items]
Total debt	$ 60,000	49,500
MWC \| Bank term loans \| Minimum
Debt Instrument [Line Items]
Rate	3.89%
MWC \| Bank term loans \| Maximum
Debt Instrument [Line Items]
Rate	6.47%
MWC \| Revolving Fund Loan \| State revolving fund loans
Debt Instrument [Line Items]
Total debt	$ 12,763	$ 14,239
MWC \| Revolving Fund Loan \| State revolving fund loans \| Minimum
Debt Instrument [Line Items]
Rate	0.00%
MWC \| Revolving Fund Loan \| State revolving fund loans \| Maximum
Debt Instrument [Line Items]
Rate	2.23%