Summary of Significant Accounting Policies (Details)			3 Months Ended
	Apr. 15, 2024 USD ($)	Jun. 28, 2023	Mar. 31, 2024 USD ($) item customer state registrant shares	Mar. 31, 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
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					$ 200,000,000
Agreement term (in years)			3 years
Sale of stock, number of shares issued in transaction (in shares) | shares			227,981
Sale of stock, consideration received on transaction			$ 16,200,000
Payments for commissions			247,000
Payments of stock issuance costs			643,000
Sale of Stock, remaining available for sale			183,500,000
Debt instrument term (in years)		5 years
Incremental expansion of borrowing capacity			60,000,000
Notes payable to banks			294,500,000			$ 291,500,000
Notes payable to banks			43,000,000			42,000,000
Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks			130,500,000
ASUS
Summary of significant accounting policies
Payments to affiliate for corporate office administrative and general costs			$ 1,600,000	$ 1,500,000
Number of contracts with 15 year contract | item			1
BVES
Summary of significant accounting policies
Payments to affiliate for corporate office administrative and general costs			$ 936,000	$ 1,300,000
Incremental expansion of borrowing capacity			$ 10,000,000
Intercompany borrowings payment term			24 months
Maximum borrowing capacity on line of credit			$ 65,000,000
BVES | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks			$ 43,000,000
BVES | Electric:
Summary of significant accounting policies
Number of customers | customer			24,800
GSWC
Summary of significant accounting policies
Incremental expansion of borrowing capacity			$ 75,000,000
Notes payable to banks			$ 164,000,000			$ 150,000,000
Intercompany borrowings payment term			24 months
GSWC | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Notes payable to banks			$ 164,000,000
GSWC | Water:
Summary of significant accounting policies
Number of customers | customer			264,200
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			$ 75,000,000
Bay State Utility Service LLC (" BSUS") | Contracted services: | Subsequent Event
Summary of significant accounting policies
JBCC approved task order value for the first year	$ 4,100,000
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			$ 349,000,000
Maximum | Syndicated Revolving Credit Facility
Summary of significant accounting policies
Current borrowing capacity			$ 165,000,000
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			$ 200,000,000