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General - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended	9 Months Ended
	Jun. 14, 2016	Nov. 24, 2015	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Balancing Account, Net				$ 16,450	$ 29,823	$ 20,462	$ 21,552	$ 38,013	$ 36,296
Increase to cash flows from operating activities				87,967	76,929
Decrease to cash flows from financing activities				10,292	(22,168)
Water reduction target goal (percent)	20.00%	30.00%
Drought surcharges
Regulatory Assets [Line Items]
Balancing Account, Net				(961)	(6,320)	(961)	$ (7,688)	$ (1,716)	$ (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				818	500
Decrease to cash flows from financing activities				$ 818	$ 500
Regulated | Drought surcharges
Regulatory Assets [Line Items]
Balancing Account, Net						$ 0

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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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=98514028&loc=d3e3521-108585

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