SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating Revenues	$ 3,332,575	$ 3,795,643
Depreciation and Amortization	(337,600)	(236,900)
Other Operating Expenses	(2,149,000)	(2,809,100)
Operating Income/(Loss)	845,973	749,573
Interest Expense	(250,749)	(194,543)
Other Income, Net	91,030	88,981
Net Income/(Loss) Attributable to Common Shareholders	521,848	491,159
Cash Flows Used for Investments in Plant	1,149,400	977,100
Assets	57,322,225		$ 55,612,245
Other
Segment Reporting Information [Line Items]
Operating Revenues	443,600	413,800
Depreciation and Amortization	(45,700)	(36,800)
Other Operating Expenses	(349,500)	(339,600)
Operating Income/(Loss)	48,400	37,400
Interest Expense	(146,100)	(85,100)
Other Income, Net	622,600	565,800
Net Income/(Loss) Attributable to Common Shareholders	540,400	516,900
Cash Flows Used for Investments in Plant	43,000	65,200
Assets	28,358,100		26,337,700
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(836,600)	(760,900)
Depreciation and Amortization	2,500	2,100
Other Operating Expenses	834,100	759,300
Operating Income/(Loss)	0	500
Interest Expense	54,700	32,000
Other Income, Net	(614,100)	(550,600)
Net Income/(Loss) Attributable to Common Shareholders	(559,400)	(518,100)
Cash Flows Used for Investments in Plant	0	0
Assets	(28,523,400)		(26,678,500)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,261,700	2,588,600
Depreciation and Amortization	(109,800)	(22,000)
Other Operating Expenses	(1,905,100)	(2,342,300)
Operating Income/(Loss)	246,800	224,300
Interest Expense	(82,500)	(69,300)
Other Income, Net	56,600	54,300
Net Income/(Loss) Attributable to Common Shareholders	168,100	165,500
Cash Flows Used for Investments in Plant	471,300	371,900
Assets	30,437,000		29,426,400
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	906,000	1,045,200
Depreciation and Amortization	(83,000)	(77,000)
Other Operating Expenses	(554,600)	(730,400)
Operating Income/(Loss)	268,400	237,800
Interest Expense	(24,500)	(21,200)
Other Income, Net	10,100	9,000
Net Income/(Loss) Attributable to Common Shareholders	190,600	170,300
Cash Flows Used for Investments in Plant	244,800	165,500
Assets	8,948,500		8,775,300
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	507,800	458,600
Depreciation and Amortization	(101,000)	(89,900)
Other Operating Expenses	(141,900)	(128,200)
Operating Income/(Loss)	264,900	240,500
Interest Expense	(40,900)	(41,500)
Other Income, Net	14,100	9,400
Net Income/(Loss) Attributable to Common Shareholders	176,700	155,100
Cash Flows Used for Investments in Plant	358,400	336,600
Assets	15,129,800		14,806,500
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	50,100	50,300
Depreciation and Amortization	(600)	(13,300)
Other Operating Expenses	(32,000)	(27,900)
Operating Income/(Loss)	17,500	9,100
Interest Expense	(11,400)	(9,400)
Other Income, Net	1,700	1,100
Net Income/(Loss) Attributable to Common Shareholders	5,400	1,500
Cash Flows Used for Investments in Plant	31,900	$ 37,900
Assets	$ 2,972,200		$ 2,944,800