Balancing and Memorandum Revenue Account, Increase (Decrease), Current Fiscal Year

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Balancing and Memorandum Revenue Account, Increase (Decrease), Year One

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No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Balancing and Memorandum Revenue Account, Increase (Decrease), Year Two

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No definition available.

+ Details

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Namespace Prefix:	sjw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Balancing and Memorandum Revenue Accounts, Percent Increase, Current Fiscal Year

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No definition available.

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Namespace Prefix:	sjw_
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- Definition

Balancing and Memorandum Revenue Accounts, Percent Increase, Year One

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No definition available.

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Namespace Prefix:	sjw_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Balancing and Memorandum Revenue Accounts, Percent Increase, Year Two

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No definition available.

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Data Type:	dtr-types:percentItemType
Balance Type:	na
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- Definition

Balancing and Memorandum Revenue Account, Refunds (Collections)

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No definition available.

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Namespace Prefix:	sjw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Regulatory Authorization For Capital Budget

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No definition available.

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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No definition available.

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Subsequent Event (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
Subsequent Event (Details) - USD ($) $ in Thousands	Oct. 11, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Subsequent Event [Line Items]
Refunds (Collections) Adjustments		$ (8,708)	$ 0	$ (26,101)	$ 6
Subsequent Event
Subsequent Event [Line Items]
2022 revenue increase	$ 25,074
2022 percent revenue increase	6.03%
2023 revenue increase	$ 12,955
2023 percent revenue increase	2.94%
2024 revenue increase	$ 16,102
2024 percent revenue increase	3.56%
Refunds (Collections) Adjustments	$ 18,174
Regulatory authorization for capital budget	$ 350,000