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Regulatory Rate Filings (Details) - USD ($)									3 Months Ended
	Jan. 20, 2020	Dec. 20, 2019	Nov. 20, 2019	Oct. 01, 2019	Sep. 30, 2019	Feb. 01, 2019	Jan. 28, 2019	Sep. 14, 2018	Mar. 31, 2020	Mar. 31, 2019	Apr. 24, 2020	Feb. 07, 2020	Jan. 28, 2020	Dec. 06, 2019	Oct. 18, 2019	Aug. 01, 2019	Jul. 26, 2019
Public Utilities, General Disclosures [Line Items]
Regulatory Asset Increase (Decrease)									$ 1,757,000	$ 611,000
Avon Water Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized WICA Surcharge, Percentage									9.31%
San Jose Water Company [Member]
Public Utilities, General Disclosures [Line Items]
CPED Calculated Double-Billing Refund								$ 4,935,000
San Jose Water Company [Member] | Minimum
Public Utilities, General Disclosures [Line Items]
CPED Proposed Penalty, Per Offense, Per Day								500
San Jose Water Company [Member] | Maximum
Public Utilities, General Disclosures [Line Items]
CPED Proposed Penalty, Per Offense, Per Day								50,000
San Jose Water Company [Member] | CPED Calculated Refund 2014-2016
Public Utilities, General Disclosures [Line Items]
CPED Calculated Service Charge Refund								2,061,000
San Jose Water Company [Member] | CPED Calculated Refund 1987-2013
Public Utilities, General Disclosures [Line Items]
CPED Calculated Service Charge Refund								$ 1,990,000
San Jose Water Company [Member] | OII No. 18-09-003 Settlement Agreement
Public Utilities, General Disclosures [Line Items]
Utility Plant Investment Commitment																	$ 5,000,000
San Jose Water Company [Member] | OII No. 18-09-003 Settlement Agreement | Maximum
Public Utilities, General Disclosures [Line Items]
Customer Credit Refund																	2,100,000
San Jose Water Company [Member] | Advice Letter No. 545 [Member]
Public Utilities, General Disclosures [Line Items]
Customer Credit Refund																	$ (5.52)
San Jose Water Company [Member] | Advice Letter No. 534 [Member]
Public Utilities, General Disclosures [Line Items]
Memorandum Account, Requested Recovery																$ 1,243,000
San Jose Water Company [Member] | Advice Letter No. 537
Public Utilities, General Disclosures [Line Items]
Memorandum Account, Requested Refund, Monthly Amount															$ 20.84
San Jose Water Company [Member] | Advice Letter No. 541 [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 8,600,000
Public Utilities, Requested Rate Increase (Decrease), Percentage			2.28%
San Jose Water Company [Member] | Application No. 19-12-002 [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Rate Filings, Requested Rate Increase, Year One														$ 2,315,000
Regulatory Rate Filings, Requested Rate Increase as Percentage of Total Revenue at Time of Request, Year One														0.61%
Regulatory Rate Filings, Requested Rate Increase, Year Two														$ 3,960,000
Regulatory Rate Filings, Proposed Rate Increase, Percent of Authorized Revenue, Year Two														1.04%
Regulatory Rate Filings, Requested Rate Increase, Year Three														$ 2,510,000
Regulatory Rate Filings, Requested Rate Increase, Percent of Authorized Revenue, Year Three														0.65%
Regulatory Rate Filings, Requested Rate Increase, Year Four														$ 341,000
Regulatory Rate Filings, Requested Rate Increase, Percent of Authorized Revenue, Year Four														0.09%
Connecticut Water Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized WICA Surcharge, Percentage									3.24%
Requested WICA Surcharge Increase (Decrease), Percentage												(0.09%)	2.60%
Requested WICA Surcharge, Percentage												5.75%	5.84%
SJWTX, Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Authorized Regulatory Surcharge, Per Thousand Gallons				$ 2.02	$ 2.19	$ 1.05	$ 0.95
Maine Water Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 371,000	$ 221,000
Public Utilities, Requested Rate Increase (Decrease), Percentage		14.70%
Maine Water Company [Member] | Minimum
Public Utilities, General Disclosures [Line Items]
Requested WISC Surcharge Increase (Decrease), Percentage	1.76%
Maine Water Company [Member] | Maximum
Public Utilities, General Disclosures [Line Items]
Requested WISC Surcharge Increase (Decrease), Percentage	3.00%
Cost of capital memorandum account
Public Utilities, General Disclosures [Line Items]
Regulatory Asset Increase (Decrease)									$ (5,000)	$ (9,000)
Subsequent Event [Member] | San Jose Water Company [Member] | Advice Letter No. 548 [Member]
Public Utilities, General Disclosures [Line Items]
Memorandum Account, Requested Recovery											$ 1,224,000

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