Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	$ 1,512	$ 272	$ 190
Opening balance, SJWNE, LLC	0	1,283	0
Charged to expense	(177)	520	430
Charged to regulatory asset	3,032	0	0
Accounts written off	(800)	(875)	(650)
Recoveries of accounts written off	324	312	302
Balance, end of period	3,891	1,512	272
Reserve for litigation and claims:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	2,898	2,181	1,892
Charged to expense	958	3,221	480
Accounts written off	(122)	(135)	1
Payments	(3,050)	(2,369)	(192)
Balance, end of period	$ 684	$ 2,898	$ 2,181

SEC Schedule, 12-09, Valuation Allowances And Reserves Charged To Regulatory Assets

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of increase (decrease) in valuation and qualifying accounts and reserves from adjustment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690

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Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column B))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column E))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690

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Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

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Amount of increase in valuation and qualifying accounts and reserves from charge to accounts other than cost and expense.

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Amount of decrease in valuation and qualifying accounts and reserves.

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- Definition

Amount of increase in valuation and qualifying accounts and reserves from recovery of amount previously written off or reestablishment of reserve previously utilized.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column C)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690

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