Benefit Plans Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plans [Abstract]
Market gains (losses)	$ 2,520,000	$ (1,388,000)
Document Period End Date	Dec. 31, 2019
Value of life insurance contracts	$ 3,829,000
Flexible Spending Plan [Abstract]
Annual maximum contribution limit under Health Care Spending Account plan	2,500
Annual maximum contribution limit under Dependent Care Spending Account plan	5,000
Deferral Plan [Abstract]
Employer contributions to deferral plan	$ 2,046,000	1,569,000	$ 1,683,000
Minimum [Member]
Pension Plans [Abstract]
Period for performance standards	3 years
Maximum [Member]
Pension Plans [Abstract]
Period for performance standards	5 years
Executive Supplemental Retirement Plan [Member]
Pension Plans [Abstract]
Projected benefit obligation	$ 41,768,000	25,380,000
Total investments made to fund SERP	7,070,000
Net periodic pension cost	3,219,000	2,905,000	2,186,000
Executives and Non-employee Directors [Member] | Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member]
Special Deferral Election Plan and Deferral Election Program [Abstract]
Deferrals by executives and non-employee directors	7,834,000	$ 4,244,000	$ 4,528,000
Connecticut Water Service, Inc. [Member] | Executives and Non-employee Directors [Member] | Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member]
Special Deferral Election Plan and Deferral Election Program [Abstract]
Deferrals by executives and non-employee directors	$ 3,801,000