SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Operating Revenues	$ 3,220,625			$ 3,063,224			$ 10,177,048	$ 8,929,321
Depreciation and Amortization	(503,600)			(610,100)			(1,833,400)	(1,188,100)
Total Operations and Maintenance	(518,341)			(510,439)			(1,473,349)	(1,437,826)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(1,510,000)			(1,330,300)			(4,592,200)	(4,242,500)
Operating Income/(Loss)	688,682			612,400			2,278,125	2,060,870
Interest Expense	(318,065)			(300,576)			(912,107)	(822,640)
Loss on Offshore Wind	(284,000)			(464,019)			(284,000)	(464,019)
Interest Income	29,400			38,900			94,200	106,000
Other Income, Net	56,400			73,700			179,300	212,900
Income Tax (Expense)/Benefit	196,982			(76,537)			(78,849)	(348,309)
Income Tax Expense				(76,600)				(348,500)
Net Income/(Loss)	369,429	$ 354,608	$ 552,668	(116,177)	$ 337,221	$ 523,728	1,276,705	744,772
Net Income								744,700
Net Income Attributable to Noncontrolling Interests	(1,880)			(1,880)			(5,639)	(5,639)
Net Income/(Loss) Attributable to Common Shareholders	367,549			(118,057)			1,271,066	739,133
Cash Flows Used for Investments in Plant							3,175,400	3,291,900
Assets	61,702,575						61,702,575		$ 59,594,529
Other
Segment Reporting Information [Line Items]
Operating Revenues	428,300			414,700			1,273,200	1,253,600
Depreciation and Amortization	(56,400)			(52,100)			(160,500)	(146,300)
Total Operations and Maintenance	(325,100)			(325,600)			(987,500)	(986,400)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(900)			(1,000)			(3,200)	(3,900)
Operating Income/(Loss)	45,900			36,000			122,000	117,000
Interest Expense	(173,700)			(177,700)			(529,000)	(484,800)
Loss on Offshore Wind	(284,000)			(464,000)			(284,000)	(464,000)
Interest Income	40,600			57,900			127,200	171,200
Other Income, Net	466,600			(9,100)			1,526,200	973,800
Income Tax (Expense)/Benefit	325,100						382,300
Income Tax Expense				40,400				62,700
Net Income/(Loss)	420,500			(516,500)			1,344,700
Net Income								375,900
Net Income Attributable to Noncontrolling Interests	0			0			0	0
Net Income/(Loss) Attributable to Common Shareholders	420,500			(516,500)			1,344,700	375,900
Cash Flows Used for Investments in Plant							197,800	180,100
Assets	28,888,700						28,888,700		29,041,100
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(830,000)			(810,600)			(2,492,600)	(2,460,400)
Depreciation and Amortization	4,100			2,800			10,400	8,100
Total Operations and Maintenance	433,700			417,600			1,284,500	1,261,800
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	392,200			390,200			1,197,700	1,190,500
Operating Income/(Loss)	0			0			0	0
Interest Expense	40,600			57,900			127,100	171,200
Loss on Offshore Wind	0			0			0	0
Interest Income	(40,600)			(57,900)			(127,200)	(171,200)
Other Income, Net	(462,200)			26,500			(1,511,800)	(923,200)
Income Tax (Expense)/Benefit	0						0
Income Tax Expense				0				0
Net Income/(Loss)	(462,200)			26,500			(1,511,900)
Net Income								(923,200)
Net Income Attributable to Noncontrolling Interests	0			0			0	0
Net Income/(Loss) Attributable to Common Shareholders	(462,200)			26,500			(1,511,900)	(923,200)
Cash Flows Used for Investments in Plant							0	0
Assets	(30,094,900)						(30,094,900)		(29,851,900)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,717,900			2,632,800			7,662,000	6,860,800
Depreciation and Amortization	(299,800)			(420,800)			(1,130,400)	(565,500)
Operations, Excluding Storm Costs	(116,700)			(109,500)			(314,900)	(331,100)
Corporate Shared Services	(110,700)			(115,900)			(332,800)	(333,400)
Storm Costs	(27,200)			(22,100)			(69,000)	(65,800)
Employee Benefits	(56,900)			(47,100)			(152,700)	(132,600)
Uncollectible Expense	(40,200)			(59,200)			(125,000)	(134,100)
Other	(39,500)			(23,000)			(106,600)	(78,400)
Total Operations and Maintenance	(391,200)			(376,800)			(1,101,000)	(1,075,400)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(1,694,000)			(1,533,900)			(4,582,400)	(4,453,900)
Operating Income/(Loss)	332,900			301,300			848,200	766,000
Interest Expense	(99,900)			(98,800)			(286,400)	(272,200)
Loss on Offshore Wind	0			0			0	0
Interest Income	23,000			33,200			75,100	89,500
Other Income, Net	39,000			32,600			113,600	99,700
Income Tax (Expense)/Benefit	(72,200)						(175,500)
Income Tax Expense				(63,600)				(158,300)
Net Income/(Loss)	222,800			204,700			575,000
Net Income								524,700
Net Income Attributable to Noncontrolling Interests	(1,200)			(1,200)			(3,400)	(3,400)
Net Income/(Loss) Attributable to Common Shareholders	221,600			203,500			571,600	521,300
Cash Flows Used for Investments in Plant							1,496,000	1,309,100
Assets	33,292,000						33,292,000		32,031,900
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	257,100			217,200			1,859,300	1,516,700
Depreciation and Amortization	(35,700)			(28,200)			(197,800)	(161,400)
Operations, Excluding Storm Costs	(50,300)			(49,300)			(137,400)	(131,400)
Corporate Shared Services	(27,800)			(26,000)			(86,100)	(79,100)
Storm Costs	0			0			0	0
Employee Benefits	(21,000)			(19,400)			(56,800)	(52,700)
Uncollectible Expense	(7,100)			(11,600)			(50,500)	(34,100)
Other	(5,900)			(5,500)			(8,800)	(16,600)
Total Operations and Maintenance	(112,100)			(111,800)			(339,600)	(313,900)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(120,200)			(104,600)			(960,900)	(752,300)
Operating Income/(Loss)	(10,900)			(27,400)			361,000	289,100
Interest Expense	(30,200)			(25,200)			(86,700)	(72,000)
Loss on Offshore Wind	0			0			0	0
Interest Income	6,300			5,600			18,800	16,200
Other Income, Net	8,000			5,800			22,400	16,300
Income Tax (Expense)/Benefit	10,000						(78,600)
Income Tax Expense				11,000				(62,200)
Net Income/(Loss)	(16,800)			(30,200)			236,900
Net Income								187,400
Net Income Attributable to Noncontrolling Interests	0			0			0	0
Net Income/(Loss) Attributable to Common Shareholders	(16,800)			(30,200)			236,900	187,400
Cash Flows Used for Investments in Plant							589,100	697,800
Assets	10,275,800						10,275,800		9,786,700
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	578,100			542,000			1,694,600	1,583,900
Depreciation and Amortization	(104,400)			(102,000)			(320,700)	(301,800)
Operations, Excluding Storm Costs	(44,300)			(38,400)			(112,800)	(105,800)
Corporate Shared Services	(19,900)			(19,200)			(58,700)	(55,500)
Storm Costs	0			0			0	0
Employee Benefits	(13,200)			(11,900)			(36,700)	(34,400)
Uncollectible Expense	0			0			0	0
Other	(20,500)			(19,900)			(49,700)	(53,700)
Total Operations and Maintenance	(97,900)			(89,400)			(257,900)	(249,400)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(80,100)			(74,200)			(222,900)	(203,200)
Operating Income/(Loss)	295,700			276,400			893,100	829,500
Interest Expense	(47,200)			(48,500)			(113,900)	(135,400)
Loss on Offshore Wind	0			0			0	0
Interest Income	100			100			300	200
Other Income, Net	4,000			11,700			25,600	37,900
Income Tax (Expense)/Benefit	(66,400)						(209,900)
Income Tax Expense				(64,100)				(189,400)
Net Income/(Loss)	186,200			175,600			595,200
Net Income								542,800
Net Income Attributable to Noncontrolling Interests	(700)			(700)			(2,200)	(2,200)
Net Income/(Loss) Attributable to Common Shareholders	185,500			174,900			593,000	540,600
Cash Flows Used for Investments in Plant							774,300	985,600
Assets	16,729,300						16,729,300		16,070,900
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	69,200			67,100			180,500	174,700
Depreciation and Amortization	(11,400)			(9,800)			(34,400)	(21,200)
Total Operations and Maintenance	(25,700)			(24,400)			(71,800)	(74,500)
Purchased Power, Purchased Natural Gas and Transmission, Other Taxes and Energy Efficiency	(7,000)			(6,800)			(20,500)	(19,700)
Operating Income/(Loss)	25,100			26,100			53,800	59,300
Interest Expense	(7,700)			(8,300)			(23,200)	(29,400)
Loss on Offshore Wind	0			0			0	0
Interest Income	0			0			0	100
Other Income, Net	1,000			6,200			3,300	8,400
Income Tax (Expense)/Benefit	500						2,900
Income Tax Expense				(300)				(1,300)
Net Income/(Loss)	18,900			23,700			36,800
Net Income								37,100
Net Income Attributable to Noncontrolling Interests	0			0			0	0
Net Income/(Loss) Attributable to Common Shareholders	18,900			$ 23,700			36,800	37,100
Cash Flows Used for Investments in Plant							118,200	$ 119,300
Assets	$ 2,611,700						$ 2,611,700		$ 2,515,800