ACQUISITION OF AQUARION AND GOODWILL - Narrative (Details) - USD ($)			12 Months Ended
	Oct. 01, 2019	Dec. 04, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Acquisition of Aquarion			$ 0	$ 0	$ 877,652,000
Operating Revenues					15,900,000
Pre-tax income					1,100,000
Impairment loss	$ 0
Aquarion Water Company
Business Acquisition [Line Items]
Consideration transferred		$ 1,675,000,000
Acquisition of Aquarion		880,000,000
Consideration transferred, liabilities incurred		795,000,000
Equity interest		745,000,000
Aquarion shareholder loan paid at closing		$ 135,000,000
Operating Revenues					$ 7,947,700,000