Sale Of Stock, Aggregate Gross Sales Price

No definition available.

Name:	sjw_SaleOfStockAggregateGrossSalesPrice
Namespace Prefix:	sjw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sale Of Stock, Total Equity Distribution Agreement Remaining

+ References

No definition available.

+ Details

Name:	sjw_SaleOfStockTotalEquityDistributionAgreementRemaining
Namespace Prefix:	sjw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sale Of Stock, Weighted Average Price Per Share

+ References

No definition available.

+ Details

Name:	sjw_SaleOfStockWeightedAveragePricePerShare
Namespace Prefix:	sjw_
Data Type:	dtr-types1:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Face amount or stated value per share of common stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockConsiderationReceivedOnTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsidiarySaleOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=sjw_AtTheMarketOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Capitalization (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	22 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Mar. 31, 2023	Feb. 28, 2023	Dec. 31, 2022
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in usd per share)	$ 0.001	$ 0.001	$ 0.001			$ 0.001
At The Market Offering
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in usd per share)				$ 0.001
Aggregate gross sales price (up to)				$ 240,000	$ 100,000
Shares issued in offering (in shares)	169,421	1,029,924	1,914,775
Weighted average price per share (in usd per share)	$ 69.57	$ 74.57	$ 74.05
Net proceeds from stock offering	$ 11,505	$ 75,284	$ 138,716
Total equity distribution	$ 98,209	$ 98,209	$ 98,209