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General - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended
	Jun. 14, 2016	Nov. 24, 2015	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Increase to cash flows from operating activities			$ 28,242	$ 32,573
Decrease to cash flows from financing activities			15,541	(5,366)
Water reduction target goal (percent)	20.00%	30.00%
Balancing Account, Net			19,989	33,294	$ 21,552	$ 36,296
Drought surcharges
Regulatory Assets [Line Items]
Balancing Account, Net			(5,054)	(512)	$ (7,688)	$ (359)
Accounting Standards Update 2016-09, Statutory Tax Withholding Component
Regulatory Assets [Line Items]
Excess tax benefit			500
Increase to cash flows from operating activities			815	486
Decrease to cash flows from financing activities			$ 815	$ 486

X

- Definition

This represents the under-collection or over-collection associated with expense changes and the revenue authorized by the CPUC to offset those expense changes. Pursuant to Section 792.5 of the California Public Utilities Code, a balancing account must be maintained for expense items for which revenue offsets have been authorized. Since the amounts in the balancing accounts must be approved by the CPUC before they can be incorporated into rates, the Company does not recognize balancing accounts in its revenue until CPUC approval occurs. It is typical for the CPUC to incorporate any over-collected and/or under-collected balances in balancing accounts into customer rates at the time rate decisions are made as part of the Company’s general rate case proceedings by assessing temporary surcredits and/or surcharges.

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- Definition

Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount

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- Definition

Water Reduction Target Goal, Percentage

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 26
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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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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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