Business Combination, Expected Future Payment

No definition available.

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

- Definition

Payments For Other Commitments

+ References

No definition available.

+ Details

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Namespace Prefix:	cwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
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+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Cash received for the settlement of litigation during the current period.

+ References

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+ Details

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

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=cwt_TycoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Commitments and Contingencies (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
Commitments and Contingencies (Details) $ in Millions	Apr. 30, 2026 USD ($)	Mar. 31, 2026 USD ($) settlement	Dec. 31, 2025 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Feb. 28, 2026 USD ($)	Nov. 30, 2025 USD ($)
Lessee, Lease, Description [Line Items]
Number of claims \| settlement		4
BVRT Utility Holding Company LLC
Lessee, Lease, Description [Line Items]
Purchase obligation							$ 45.0
Initial payment		$ 7.0
Expected future payment		$ 3.8
Nexus Water Group
Lessee, Lease, Description [Line Items]
Purchase obligation						$ 218.0
3M Company
Lessee, Lease, Description [Line Items]
Proceeds from legal settlements			$ 34.8
DuPont
Lessee, Lease, Description [Line Items]
Proceeds from legal settlements			$ 6.1
Tyco \| Subsequent Event
Lessee, Lease, Description [Line Items]
Proceeds from legal settlements	$ 6.5
BASF \| Subsequent Event
Lessee, Lease, Description [Line Items]
Proceeds from legal settlements	$ 2.7
Supply Commitment \| Camino Real
Lessee, Lease, Description [Line Items]
Payments for other commitments				$ 22.3	$ 21.5