SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating Revenues	$ 3,063,224	$ 2,791,482		$ 8,929,321	$ 9,216,467
Depreciation and Amortization	(610,100)	(185,500)		(1,188,100)	(524,000)
Other Operating Expenses	(1,840,700)	(2,075,400)		(5,680,300)	(6,851,700)
Operating Income/(Loss)	612,400	530,553		2,060,870	1,840,787
Interest Expense	(300,600)	(222,300)		(822,600)	(624,100)
Loss on Offshore Wind Investments	(464,019)	0	$ (401,000)	(464,019)	(401,000)	$ (1,770,000)
Other Income, Net	112,555	79,123		318,870	262,980
Net Income/(Loss) Attributable to Common Shareholders	(118,057)	339,663		739,133	846,245
Cash Flows Used for Investments in Plant				3,291,900	3,125,600
Assets	58,573,319			58,573,319		55,612,245
Other
Segment Reporting Information [Line Items]
Operating Revenues	414,700	394,700		1,253,600	1,217,300
Depreciation and Amortization	(52,100)	(40,700)		(146,300)	(115,500)
Other Operating Expenses	(326,600)	(315,700)		(990,300)	(992,600)
Operating Income/(Loss)	36,000	38,300		117,000	109,200
Interest Expense	(177,700)	(111,400)		(484,800)	(297,000)
Loss on Offshore Wind Investments	(464,000)			(464,000)	(401,000)
Other Income, Net	48,800	415,900		1,145,000	1,082,600
Net Income/(Loss) Attributable to Common Shareholders	(516,500)	397,000		375,900	621,600
Cash Flows Used for Investments in Plant				180,100	207,100
Assets	27,371,000			27,371,000		26,337,700
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(810,600)	(753,000)		(2,460,400)	(2,295,100)
Depreciation and Amortization	2,800	2,300		8,100	6,600
Other Operating Expenses	807,800	751,200		2,452,300	2,290,000
Operating Income/(Loss)	0	500		0	1,500
Interest Expense	57,900	38,400		171,200	104,800
Loss on Offshore Wind Investments	0			0	0
Other Income, Net	(31,400)	(412,700)		(1,094,400)	(1,038,000)
Net Income/(Loss) Attributable to Common Shareholders	26,500	(373,800)		(923,200)	(931,700)
Cash Flows Used for Investments in Plant				0	0
Assets	(28,533,900)			(28,533,900)		(26,678,500)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,632,800	2,371,300		6,860,800	7,014,300
Depreciation and Amortization	(420,800)	(700)		(565,500)	59,300
Other Operating Expenses	(1,910,700)	(2,124,000)		(5,529,300)	(6,371,400)
Operating Income/(Loss)	301,300	246,600		766,000	702,200
Interest Expense	(98,800)	(76,800)		(272,200)	(214,400)
Loss on Offshore Wind Investments	0			0	0
Other Income, Net	65,800	53,500		189,200	155,700
Net Income/(Loss) Attributable to Common Shareholders	203,500	173,300		521,300	504,300
Cash Flows Used for Investments in Plant				1,309,100	1,230,300
Assets	31,411,300			31,411,300		29,426,400
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	217,200	218,300		1,516,700	1,672,600
Depreciation and Amortization	(28,200)	(38,000)		(161,400)	(156,700)
Other Operating Expenses	(216,400)	(211,100)		(1,066,200)	(1,280,800)
Operating Income/(Loss)	(27,400)	(30,800)		289,100	235,100
Interest Expense	(25,200)	(19,700)		(72,000)	(62,400)
Loss on Offshore Wind Investments	0			0	0
Other Income, Net	11,400	9,200		32,500	27,900
Net Income/(Loss) Attributable to Common Shareholders	(30,200)	(33,700)		187,400	148,200
Cash Flows Used for Investments in Plant				697,800	536,800
Assets	9,518,200			9,518,200		8,775,300
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	542,000	491,600		1,583,900	1,430,400
Depreciation and Amortization	(102,000)	(94,500)		(301,800)	(276,400)
Other Operating Expenses	(163,600)	(144,900)		(452,600)	(409,400)
Operating Income/(Loss)	276,400	252,200		829,500	744,600
Interest Expense	(48,500)	(43,000)		(135,400)	(126,700)
Loss on Offshore Wind Investments	0			0	0
Other Income, Net	11,800	11,900		38,100	30,800
Net Income/(Loss) Attributable to Common Shareholders	174,900	160,300		540,600	476,400
Cash Flows Used for Investments in Plant				985,600	1,011,300
Assets	15,750,500			15,750,500		14,806,500
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	67,100	68,600		174,700	177,000
Depreciation and Amortization	(9,800)	(13,900)		(21,200)	(41,300)
Other Operating Expenses	(31,200)	(30,900)		(94,200)	(87,500)
Operating Income/(Loss)	26,100	23,800		59,300	48,200
Interest Expense	(8,300)	(9,800)		(29,400)	(28,400)
Loss on Offshore Wind Investments	0			0	0
Other Income, Net	6,200	1,300		8,500	4,000
Net Income/(Loss) Attributable to Common Shareholders	23,700	$ 16,600		37,100	27,400
Cash Flows Used for Investments in Plant				119,300	$ 140,100
Assets	$ 3,056,200			$ 3,056,200		$ 2,944,800