Summary of Significant Accounting Policies (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Aug. 01, 2024 USD ($)	Jul. 01, 2024 USD ($)	Apr. 15, 2024 USD ($)	Jun. 30, 2024 USD ($) state item shares	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) customer state registrant item shares	Jun. 30, 2023 USD ($)	Feb. 27, 2024 USD ($)	Dec. 31, 2023 USD ($)
Summary of significant accounting policies
Number of customers | customer						1,000,000
Number of states in which entity operates | state				10		10
Number of military bases started operating in April 2024 | item						2
Number of registrants filing combined report | registrant						2
Sale of stock, maximum consideration on transaction								$ 200,000
Agreement term (in years)						3 years
Sale of stock, number of shares issued in transaction (in shares) | shares				227,667		455,648
Sale of stock, consideration received on transaction				$ 16,800		$ 33,000
Payments for commissions				300		500
Payments of stock issuance costs				100		700
Sale of Stock, remaining available for sale				166,500		$ 166,500
Debt instrument term (in years)						5 years
Notes payable to banks				128,000		$ 128,000			$ 291,500
Notes payable to banks				167,000		167,000			42,000
Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks				128,000		128,000
ASUS
Summary of significant accounting policies
Payments to affiliate for corporate office administrative and general costs				1,200	$ 1,200	2,800	$ 2,700
BVES
Summary of significant accounting policies
Payments to affiliate for corporate office administrative and general costs				700	$ 700	$ 1,700	$ 2,100
Intercompany borrowings payment term						24 months
Maximum borrowing capacity on line of credit				65,000		$ 65,000
BVES | Financing Application [Member] | Subsequent Event
Summary of significant accounting policies
Regulatory Rate Case Filings Requested Authorization For Debt And Equity Issuance Amount	$ 120,000
Regulatory Rate Filings, Requested Deferment Period	9 months
BVES | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks				48,000		$ 48,000
BVES | Electric:
Summary of significant accounting policies
Number of customers | customer						24,800
GSWC
Summary of significant accounting policies
Notes payable to banks				0		$ 0			150,000
Intercompany borrowings payment term						24 months
Notes payable to banks				119,000		$ 119,000			$ 0
GSWC | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks				119,000		119,000
GSWC | Unsecured Private Placement Notes
Summary of significant accounting policies
Face amount of debt				$ 65,000		$ 65,000
Debt Instrument, Interest Rate, Stated Percentage				5.50%		5.50%
GSWC | Water:
Summary of significant accounting policies
Number of customers | customer						264,400
Bay State Utility Service LLC (" BSUS")
Summary of significant accounting policies
Number of contracts with 15 year contract | item				1		1
Bay State Utility Service LLC (" BSUS") | Contracted services:
Summary of significant accounting policies
Period of fixed price contracts to operate and maintain water systems at various military bases						15 years
Initial price contract value				$ 75,000
JBCC approved task order value for the first year			$ 4,100
Patuxent River Utility Services LLC ( PRUS) | Contracted services:
Summary of significant accounting policies
Period of fixed price contracts to operate and maintain water systems at various military bases						50 years
Initial price contract value						$ 349,000
Patuxent River Utility Services LLC ( PRUS) | Contracted services: | Subsequent Event
Summary of significant accounting policies
Revised price contract value after an inventory adjustment		$ 378,000
Maximum | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Current borrowing capacity				165,000		$ 165,000
Maximum | ASUS
Summary of significant accounting policies
Period of fixed price contracts to operate and maintain water systems at various military bases						50 years
Maximum | GSWC | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Current borrowing capacity				$ 200,000		$ 200,000