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v3.21.2

Fair Value of Financial Assets and Liabilities - Narrative (Details) | 9 Months Ended
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Sep. 30, 2021
Fair Value Disclosures [Abstract] |
Risk premium (as a percent) | 0.60%

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- Definition Represents the risk premium rate as an input to measure fair value. + References No definition available. + Details
Name: | cwt_FairValueInputsRiskPremium
Namespace Prefix: | cwt_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_FairValueDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration