Commitments (Details) $ / yr in Thousands, $ in Thousands						1 Months Ended	12 Months Ended
	Jun. 16, 2022	Feb. 01, 2022	Nov. 07, 2020	Nov. 06, 2020	May 19, 2003	Dec. 31, 2022 USD ($) employee acre_foot $ / million_gallons $ / ft³ gal	Dec. 31, 2022 USD ($) employee acre_foot $ / ft³ $ / million_gallons gal	Dec. 31, 2021 USD ($) $ / million_gallons gal	Dec. 31, 2020 USD ($) gal	Dec. 31, 2008 $ / yr gal	Dec. 31, 1997	Feb. 25, 2022 USD ($)	Jan. 08, 2020 USD ($)
Long-term Purchase Commitment [Line Items]
Purchased water							$ 122,334	$ 98,231	$ 100,723
Intangible assets						$ 35,959	$ 35,959	$ 36,276
Union Member
Long-term Purchase Commitment [Line Items]
Collective bargaining agreement percent of wage increase for 2023						6.00%	6.00%
Collective bargaining agreement percent of wage increase for 2024						3.50%	3.50%
Collective bargaining agreement percent of wage increase for 2025						5.50%	5.50%
SJW Group
Long-term Purchase Commitment [Line Items]
Number of employees | employee						362	362
SJW Group | Union Member
Long-term Purchase Commitment [Line Items]
Number of employees | employee						215	215
Minimum
Long-term Purchase Commitment [Line Items]
Useful life of intangible assets							5 years
Maximum
Long-term Purchase Commitment [Line Items]
Useful life of intangible assets							70 years
RWA | Capacity Agreement
Long-term Purchase Commitment [Line Items]
Current contract water rate (in USD per million of gallons)								2,600		75
Purchase commitment period										14 years
RWA | Capacity Agreement | Minimum
Long-term Purchase Commitment [Line Items]
Purchase commitment period										50 years
RWA | Capacity Agreement | Maximum
Long-term Purchase Commitment [Line Items]
Agreement to purchase water (in gallons of water) | gal										1,000,000
MDC | Capacity Agreement
Long-term Purchase Commitment [Line Items]
Current contract water rate (in USD per million of gallons) | $ / ft³						4.09	4.09
Purchase commitment period					50 years
Agreement to purchase water (in gallons of water) | gal								283,000,000
Kennebec Water District
Long-term Purchase Commitment [Line Items]
Agreement to purchase water (in gallons of water) | gal							50,000,000
Contract agreement, term			20 years	20 years
Long-term purchase commitment, wholesale discount (in USD per hundred cubic feet) | $ / ft³						0.20	0.20
Tariff rate (in USD per hundred cubic feet) | $ / ft³							1.51
International Union of Operating Engineers | SJW Group
Long-term Purchase Commitment [Line Items]
Bargaining agreements, term						3 years
Service Agreements
Long-term Purchase Commitment [Line Items]
Useful life of intangible assets											25 years
Intangible assets						$ 4,304	$ 4,304
Concession fees
Long-term Purchase Commitment [Line Items]
Lease renewal term												2 years
Intangible assets						$ 6,800	$ 6,800	$ 6,800				$ 1,600	$ 5,000
Santa Clara Valley Water District
Long-term Purchase Commitment [Line Items]
Master contract, negotiated term for delivery schedules							3 years
Water purchased (in millions of gallons) | gal							18,183,000,000	19,365,000,000	21,269,000,000
Purchased water							$ 96,793	$ 91,938	$ 96,212
Reduction in delivery schedule, percent	23.00%
Increase in delivery schedule, percent		10.00%
Minimum percent of delivery schedule to be purchased						90.00%	90.00%
Minimum volume of water to be purchased (in million gallons) | gal						18,864,000,000	18,864,000,000
Cost of water to be purchased						$ 106,463	$ 106,463
Current contract water rate (in USD per million of gallons) | $ / million_gallons						5,600	5,600
Guadalupe-Blanco River Authority | SJWTX, Inc.
Long-term Purchase Commitment [Line Items]
Long-term purchase commitment, minimum area required (in acre-feet of water) | acre_foot						7,650	7,650
Notice period required for contract adjustment							60 days
Lower Colorado River Authority | SJWTX, Inc.
Long-term Purchase Commitment [Line Items]
Long-term purchase commitment, minimum area required (in acre-feet of water) | acre_foot						350	350