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Benefit Plans - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]      
Adjustment to pension benefit plans, net of taxes $ 216,000 $ (2,151,000) $ (716,000)
Value of life insurance contracts 3,937,000 3,420,000  
Annual maximum contribution limit under Health Care Spending Account plan 3,100    
Annual maximum contribution limit under Dependent Care Spending Account plan 5,000    
Employer contributions to deferral plan $ 3,902,000 3,003,000 2,822,000
Health care cost trend rate assumed, next fiscal year 8.00%    
Ultimate health care cost trend rate 4.50%    
Actuarial gain (loss), discount rate change $ (1,188,000) 116,372,000  
Actuarial gain (loss), data and other changes (1,993,000) (12,422,000)  
Actuarial gain (loss), mortality change (168,000) 4,000  
Defined benefit plan, accumulated benefit obligation 270,209,000 259,838,000  
Unrecognized pensions and other postretirement benefits      
Defined Benefit Plan Disclosure [Line Items]      
Regulatory liabilities 20,196,000 14,307,000  
Other comprehensive income (loss), defined benefit plan, gain (loss) arising during period 20,196,000 14,307,000  
Unrecognized pensions and other postretirement benefits      
Defined Benefit Plan Disclosure [Line Items]      
Regulatory assets 24,593,000 45,799,000  
Other comprehensive income (loss), defined benefit plan, gain (loss) arising during period (24,552,000) (45,743,000)  
Other comprehensive (income) loss, defined benefit plan, prior service cost (credit) 41,000 56,000  
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Projected benefit obligation 297,834,000 289,123,000 383,838,000
Net periodic pension cost 8,588,000 4,268,000 8,068,000
Total investments made to fund SERP 11,145,000 11,712,000  
Executive Supplemental Retirement Plan      
Defined Benefit Plan Disclosure [Line Items]      
Projected benefit obligation 43,001,000 39,455,000  
Net periodic pension cost 3,257,000 4,400,000 4,456,000
Adjustment to pension benefit plans, net of taxes 314,000 1,640,000 $ 901,000
Total investments made to fund SERP $ 6,843,000 $ 6,395,000  
Minimum      
Defined Benefit Plan Disclosure [Line Items]      
Period for performance standards 3 years    
Minimum | Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Net periodic benefit cost, expected return on plan assets 6.00% 6.50% 6.50%
Maximum      
Defined Benefit Plan Disclosure [Line Items]      
Period for performance standards 5 years    
Maximum | Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Net periodic benefit cost, expected return on plan assets 6.75% 6.75% 6.75%
CTWS Employees      
Defined Benefit Plan Disclosure [Line Items]      
Rate of compensation increase to company sponsored savings plan 1.50%    
Executives and Non-employee Directors | Deferred compensation arrangement with individual, by type of compensation, pension and other postretirement benefits      
Defined Benefit Plan Disclosure [Line Items]      
Deferrals by executives and non-employee directors $ 8,148,000 $ 6,197,000  
Executives and Non-employee Directors | Deferred compensation arrangement with individual, by type of compensation, pension and other postretirement benefits | Connecticut Water Company      
Defined Benefit Plan Disclosure [Line Items]      
Deferrals by executives and non-employee directors $ 6,223,000 $ 4,508,000