Represents the number of facilities taken under operating lease.

No definition available.

Name:	cwt_OperatingLeasesNumberOfFacilitiesLeased
Namespace Prefix:	cwt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the revenue received in exchange for handling the system and system improvements under operating leases.

+ References

No definition available.

+ Details

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

- Definition

Represents the term of lease agreement entered into by the entity to operate the water system.

+ References

No definition available.

+ Details

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Namespace Prefix:	cwt_
Data Type:	us-types:durationStringItemType
Balance Type:	na
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- Details

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Balance Type:	na
Period Type:	duration

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 122

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 3)

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-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fifth year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

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

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fourth year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

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Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

This element represents the payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 25

-Paragraph 5

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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

- Definition

The cash outflow for acquisition of or capital improvements to properties held for investment (operating, managed, leased) or for use.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-Paragraph 13

-Subparagraph (c)

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-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8,17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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COMMITMENTS AND CONTINGENCIES (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Oct. 31, 2011	Dec. 31, 2011 lease	Dec. 31, 2010	Dec. 31, 2009
Office Leases
Lease Commitments
2012		$ 807
2013		616
2014		512
2015		396
2016		296
Thereafter		2,711
Other lease commitment disclosures
Annual lease payments made and charged		1,271	1,080	986
System Leases
Lease Commitments
Number of water systems leased		2
2012		845
2013		845
2014		845
2015		845
2016		845
Thereafter		1,338
Hawthorne lease
Lease Commitments
Number of water systems leased		3
Other lease commitment disclosures
Annual lease payments made and charged		940
Lease term (in years)	15 years
Lease deposit		8,100
Revenue from the water system received in exchange for handling of system and system improvements		7,506	7,547	6,111
Annual payments made under capital improvements		537	116	116
Hawthorne lease \| Minimum
Other lease commitment disclosures
Annual lease payments made and charged		940
Commerce
Other lease commitment disclosures
Lease term (in years)		15 years
Annual lease payment		$ 845