The high end of range of percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

The low end of range of percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ Details

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- Definition

Maximum period within which all short term borrowings need to be repaid.

+ Details

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- Definition

The high end of the range of the fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ Details

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- Definition

The low end of the range of the fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ Details

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- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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- 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.

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- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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- 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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

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

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- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ 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 210.5-02.22(a)(1))

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

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Short-term and Long-term Borrowings (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		1 Months Ended	9 Months Ended
	Sep. 30, 2011 segment M D Y	Jun. 30, 2011 California Water Service Group and subsidiaries	Jun. 30, 2011 California Water Service Group	Sep. 30, 2011 California Water Service Group	Dec. 31, 2010 California Water Service Group	Sep. 30, 2010 California Water Service Group	Jun. 30, 2011 Cal Water	Jun. 29, 2011 California Water Service Group and Cal Water
Short-term and Long-term Borrowings
Maximum borrowing capacity under the short-term credit facility		$ 100					$ 300	$ 400
Period within which borrowings are to be repaid (in months)	12
Basis of interest rate				LIBOR
Interest rate margin, low end of range (as a percent)			0.725%
Interest rate margin, high end of range (as a percent)			0.95%
Commitment fee, low end of range (as a percent)			0.08%
Commitment fee, high end of range (as a percent)			0.125%
Outstanding borrowings under lines of credit facility				$ 39.9	$ 23.8
Average borrowing rate (as a percent)				2.60%		3.00%