Capitalization - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	Feb. 28, 2026 USD ($)	May 31, 2025 USD ($)	May 31, 2024 USD ($) loan	Mar. 31, 2026 USD ($) $ / shares shares	Mar. 31, 2025 USD ($) shares	Dec. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)
Class of Stock [Line Items]
At-The-Market Program Common Stock Issuance				$ 2,662
Proceeds from Issuance of Common Stock				2,819	$ 221
Proceeds from Issuance of Long-term Debt				1,496	$ 28
Secured Debt | Pinelands Water Company
Class of Stock [Line Items]
Interest rate	6.17%
Debt repaid	$ 3,700
Secured Debt | Pinelands Wastewater Company
Class of Stock [Line Items]
Interest rate	6.17%
Debt repaid	$ 3,400
September 2024 Delaware SRF | Loans Payable | Tidewater
Class of Stock [Line Items]
Borrowing amount							$ 2,200
Interest rate							0.00%
Proceeds from Issuance of Long-term Debt				1,800
May 2024 Delaware SRF | Loans Payable | Tidewater
Class of Stock [Line Items]
Borrowing amount			$ 5,600
Interest rate			2.00%
Proceeds from Issuance of Long-term Debt				2,100
Number of debt instruments | loan			4
December 2025 Delaware State Revolving Fund | Loans Payable | Tidewater
Class of Stock [Line Items]
Borrowing amount						$ 1,000
Interest rate						2.00%
December 2025 Delaware State Revolving Fund | Loans Payable | Southern Shores
Class of Stock [Line Items]
Borrowing amount						$ 400
Interest rate						0.00%
Proceeds from Issuance of Long-term Debt				200
Amortizing Secured Notes And State Revolving Trust Notes | Loans Payable
Class of Stock [Line Items]
Carrying amount of debt				252,800		$ 259,500
Construction Advances | Loans Payable
Class of Stock [Line Items]
Carrying amount of debt				$ 26,000		$ 25,500
ATM Equity Sales Agreement
Class of Stock [Line Items]
Aggregate gross sales price		$ 110,000
Number of shares issued and sold under agreement (in shares) | shares				49,305
Weighted average price per share of shares issued and sold under agreement (in dollars per share) | $ / shares				$ 54.82
Proceeds from Issuance of Common Stock				$ 2,700
Aggregate gross sales price of shares remaining to be issued under agreement				$ 77,300
Common Stock
Class of Stock [Line Items]
Number of common shares issued (in shares) | shares				49,000
At-The-Market Program Common Stock Issuance				$ 2,662
Middlesex Water Company Investment Plan | Common Stock
Class of Stock [Line Items]
Number of common shares issued (in shares) | shares				4,025	4,228
At-The-Market Program Common Stock Issuance				$ 200	$ 200