SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,791,482		$ 3,215,645	$ 9,216,467	$ 9,259,596
Depreciation and Amortization	(185,500)		(413,400)	(524,000)	(1,304,400)
Other Operating Expenses	(2,075,400)		(2,244,900)	(6,851,700)	(6,279,300)
Operating Income/(Loss)	530,553		557,293	1,840,787	1,675,917
Interest Expense	(222,283)		(178,174)	(624,140)	(491,509)
Impairment of Offshore Wind Investment	0	$ (401,000)	0	(401,000)	0
Other Income, Net	79,123		89,831	262,980	255,253
Net Income/(Loss) Attributable to Common Shareholders	339,663		349,409	846,245	1,084,717
Cash Flows Used for Investments in Plant				3,125,617	2,352,743
Assets	56,293,343			56,293,343		$ 53,230,900
Other
Segment Reporting Information [Line Items]
Operating Revenues	394,700		343,500	1,217,300	1,062,700
Depreciation and Amortization	(40,700)		(35,400)	(115,500)	(98,800)
Other Operating Expenses	(315,700)		(265,700)	(992,600)	(876,500)
Operating Income/(Loss)	38,300		42,400	109,200	87,400
Interest Expense	(111,400)		(69,600)	(297,000)	(169,900)
Impairment of Offshore Wind Investment				(401,000)
Other Income, Net	415,900		429,900	1,082,600	1,280,100
Net Income/(Loss) Attributable to Common Shareholders	397,000		379,000	621,600	1,163,600
Cash Flows Used for Investments in Plant				207,100	177,600
Assets	29,019,000			29,019,000		26,365,200
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(753,000)		(682,500)	(2,295,100)	(2,088,100)
Depreciation and Amortization	2,300		1,800	6,600	5,100
Other Operating Expenses	751,200		681,100	2,290,000	2,081,900
Operating Income/(Loss)	500		400	1,500	(1,100)
Interest Expense	38,400		20,000	104,800	46,300
Impairment of Offshore Wind Investment				0
Other Income, Net	(412,700)		(423,000)	(1,038,000)	(1,251,500)
Net Income/(Loss) Attributable to Common Shareholders	(373,800)		(402,600)	(931,700)	(1,206,300)
Cash Flows Used for Investments in Plant				0	0
Assets	(27,549,600)			(27,549,600)		(24,737,500)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,371,300		2,795,100	7,014,300	7,185,800
Depreciation and Amortization	(700)		(256,900)	59,300	(806,700)
Other Operating Expenses	(2,124,000)		(2,261,500)	(6,371,400)	(5,743,200)
Operating Income/(Loss)	246,600		276,700	702,200	635,900
Interest Expense	(76,800)		(64,500)	(214,400)	(184,200)
Impairment of Offshore Wind Investment				0
Other Income, Net	53,500		59,600	155,700	160,100
Net Income/(Loss) Attributable to Common Shareholders	173,300		225,100	504,300	495,000
Cash Flows Used for Investments in Plant				1,230,300	823,900
Assets	28,840,900			28,840,900		27,365,000
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	218,300		225,600	1,672,600	1,569,400
Depreciation and Amortization	(38,000)		(25,100)	(156,700)	(116,200)
Other Operating Expenses	(211,100)		(226,300)	(1,280,800)	(1,244,300)
Operating Income/(Loss)	(30,800)		(25,800)	235,100	208,900
Interest Expense	(19,700)		(18,800)	(62,400)	(51,200)
Impairment of Offshore Wind Investment				0
Other Income, Net	9,200		11,100	27,900	31,900
Net Income/(Loss) Attributable to Common Shareholders	(33,700)		(24,600)	148,200	147,200
Cash Flows Used for Investments in Plant				536,800	424,500
Assets	8,404,500			8,404,500		8,084,900
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	491,600		468,800	1,430,400	1,361,600
Depreciation and Amortization	(94,500)		(85,100)	(276,400)	(250,300)
Other Operating Expenses	(144,900)		(143,700)	(409,400)	(414,300)
Operating Income/(Loss)	252,200		240,000	744,600	697,000
Interest Expense	(43,000)		(36,600)	(126,700)	(107,300)
Impairment of Offshore Wind Investment				0
Other Income, Net	11,900		10,100	30,800	28,300
Net Income/(Loss) Attributable to Common Shareholders	160,300		155,800	476,400	455,800
Cash Flows Used for Investments in Plant				1,011,300	823,300
Assets	14,693,400			14,693,400		13,369,500
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	68,600		65,100	177,000	168,200
Depreciation and Amortization	(13,900)		(12,700)	(41,300)	(37,500)
Other Operating Expenses	(30,900)		(28,800)	(87,500)	(82,900)
Operating Income/(Loss)	23,800		23,600	48,200	47,800
Interest Expense	(9,800)		(8,700)	(28,400)	(25,200)
Impairment of Offshore Wind Investment				0
Other Income, Net	1,300		2,100	4,000	6,400
Net Income/(Loss) Attributable to Common Shareholders	16,600		$ 16,700	27,400	29,400
Cash Flows Used for Investments in Plant				140,100	$ 103,400
Assets	$ 2,885,100			$ 2,885,100		$ 2,783,800