Line of Credit Facility, Incremental Expansion of Borrowing Capacity

No definition available.

Name:	cwt_LineofCreditFacilityIncrementalExpansionofBorrowingCapacity
Namespace Prefix:	cwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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:	us-gaap_DebtInstrumentAxis=cwt_Series1MortgageBondsMember
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Short-term and Long-term Borrowings (Details) - USD ($)			3 Months Ended
Short-term and Long-term Borrowings (Details) - USD ($)	May 11, 2021	Mar. 29, 2019	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Cal Water
Debt Instrument [Line Items]
Outstanding borrowings			$ 15,000,000		$ 0
Parent Company
Debt Instrument [Line Items]
Outstanding borrowings			$ 35,000,000		$ 35,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 550,000,000
Debt instrument, term		5 years
Average borrowing rate			0.98%	0.98%
Revolving Credit Facility \| Cal Water
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 400,000,000
Incremental expansion of borrowing capacity		150,000,000
Revolving Credit Facility \| Parent Company
Debt Instrument [Line Items]
Maximum borrowing capacity		150,000,000
Incremental expansion of borrowing capacity		$ 50,000,000
Secured Debt
Debt Instrument [Line Items]
Debt issued	$ 280,000,000
Secured Debt \| Series ZZZ Mortgage Bonds
Debt Instrument [Line Items]
Debt issued	$ 130,000,000
Interest rate	2.87%
Secured Debt \| Series 1 Mortgage Bonds
Debt Instrument [Line Items]
Debt issued	$ 150,000,000
Interest rate	3.02%