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Public Utilities, Number of Communities Served

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Public Utilities, Service Area

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Public Utilities, Service Connections

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Variable Interest Entities, Number Of Entities

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

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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.

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Useful life on which depreciation was computed for entities with a substantial portion of business acquiring and holding investment real estate, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

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Summary of Significant Accounting Policies - Narrative (Details) service_connection in Thousands, people in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) mi² entity service_connection people subsidiary community	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Number of variable interest entities \| entity	2
Impairment of Long-Lived Assets Held-for-use \| $	$ 0	$ 0	$ 0
Goodwill, Impairment Loss \| $	$ 0	$ 0	$ 0
Minimum
Public Utilities, General Disclosures [Line Items]
Service area in square miles \| mi²	247
Minimum \| Finite-Lived Intangible Assets
Public Utilities, General Disclosures [Line Items]
Estimated useful life	7 years
Maximum \| Finite-Lived Intangible Assets
Public Utilities, General Disclosures [Line Items]
Estimated useful life	12 years
Revenues \| Product Concentration Risk
Public Utilities, General Disclosures [Line Items]
Percentage of revenue derived from sales of water to business and residential customers	93.00%
San Jose Water Company
Public Utilities, General Disclosures [Line Items]
Public Utilities, Service Connections \| service_connection	231
Number of people served \| people	1,000,000,000
Connecticut Water Service, Inc.
Public Utilities, General Disclosures [Line Items]
Number of people served \| people	485
Public Utilities, Number of Communities Served \| community	81
Acequia Water Supply Corporation
Public Utilities, General Disclosures [Line Items]
Ownership percentage in Acequia Water Supply Corporation	25.00%
444 West Santa Clara Street, L.P. \| 444 West Santa Clara Street, L.P.
Public Utilities, General Disclosures [Line Items]
Limited partnership interest percentage	70.00%
San Jose Water Company
Public Utilities, General Disclosures [Line Items]
Number of subsidiaries that are primary beneficiaries \| subsidiary	2
SJWTX, Inc. dba Canyon Lake Water Supply Corporation
Public Utilities, General Disclosures [Line Items]
Number of people served \| people	59
Connecticut and Maine \| Connecticut Water Service, Inc.
Public Utilities, General Disclosures [Line Items]
Public Utilities, Service Connections \| service_connection	139
Connecticut \| Connecticut Water Service, Inc.
Public Utilities, General Disclosures [Line Items]
Public Utilities, Service Connections \| service_connection	3