Summary of Significant Accounting Policies - Cash and Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 23, 2020
Public Utilities, General Disclosures [Line Items]
Total debt	$ 1,583,441	$ 1,488,788
Maine Water Company
Public Utilities, General Disclosures [Line Items]
Total debt	$ 64,639	66,999
Cash			$ 2,789
Restricted Cash and Cash Equivalents, Current		$ 1,211
Maine Water Company | State Revolving Fund Loans Series T | Public utility, bonds
Public Utilities, General Disclosures [Line Items]
Total debt				$ 4,000