SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating Revenues	$ 3,215,645	$ 2,432,794	$ 9,259,596	$ 7,381,172
Depreciation and Amortization	(413,400)	(322,100)	(1,304,400)	(981,100)
Other Operating Expenses	(2,244,900)	(1,627,400)	(6,279,300)	(4,879,600)
Operating Income/(Loss)	557,293	483,331	1,675,917	1,520,503
Interest Expense	(178,174)	(147,962)	(491,509)	(431,162)
Other Income, Net	89,831	43,768	255,253	124,588
Net Income/(Loss) Attributable to Common Shareholders	349,409	283,166	1,084,717	913,829
Cash Flows Used for Investments in Plant			2,352,743	2,211,136
Assets	51,599,425		51,599,425		$ 48,492,144
Other
Segment Reporting Information [Line Items]
Operating Revenues	343,500	326,100	1,062,700	999,100
Depreciation and Amortization	(35,400)	(28,000)	(98,800)	(83,700)
Other Operating Expenses	(265,700)	(275,200)	(876,500)	(860,300)
Operating Income/(Loss)	42,400	22,900	87,400	55,100
Interest Expense	(69,600)	(42,500)	(169,900)	(125,900)
Other Income, Net	429,900	325,900	1,280,100	1,059,200
Net Income/(Loss) Attributable to Common Shareholders	379,000	304,900	1,163,600	982,500
Cash Flows Used for Investments in Plant			177,600	157,600
Assets	24,865,400		24,865,400		22,674,700
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(682,500)	(614,100)	(2,088,100)	(1,918,900)
Depreciation and Amortization	1,800	1,100	5,100	3,100
Other Operating Expenses	681,100	613,700	2,081,900	1,918,900
Operating Income/(Loss)	400	700	(1,100)	3,100
Interest Expense	20,000	12,700	46,300	37,000
Other Income, Net	(423,000)	(320,400)	(1,251,500)	(1,046,200)
Net Income/(Loss) Attributable to Common Shareholders	(402,600)	(307,000)	(1,206,300)	(1,006,100)
Cash Flows Used for Investments in Plant			0	0
Assets	(23,804,400)		(23,804,400)		(21,738,600)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,795,100	2,055,200	7,185,800	5,632,100
Depreciation and Amortization	(256,900)	(179,800)	(806,700)	(534,100)
Other Operating Expenses	(2,261,500)	(1,640,500)	(5,743,200)	(4,531,300)
Operating Income/(Loss)	276,700	234,900	635,900	566,700
Interest Expense	(64,500)	(61,000)	(184,200)	(175,400)
Other Income, Net	59,600	25,400	160,100	76,000
Net Income/(Loss) Attributable to Common Shareholders	225,100	150,400	495,000	365,400
Cash Flows Used for Investments in Plant			823,900	764,900
Assets	26,992,600		26,992,600		25,411,200
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	225,600	185,500	1,569,400	1,277,800
Depreciation and Amortization	(25,100)	(28,500)	(116,200)	(108,700)
Other Operating Expenses	(226,300)	(176,900)	(1,244,300)	(970,600)
Operating Income/(Loss)	(25,800)	(19,900)	208,900	198,500
Interest Expense	(18,800)	(15,700)	(51,200)	(44,200)
Other Income, Net	11,100	6,700	31,900	15,200
Net Income/(Loss) Attributable to Common Shareholders	(24,600)	(22,000)	147,200	129,600
Cash Flows Used for Investments in Plant			424,500	506,400
Assets	7,692,600		7,692,600		7,215,900
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	468,800	418,300	1,361,600	1,230,100
Depreciation and Amortization	(85,100)	(75,400)	(250,300)	(223,400)
Other Operating Expenses	(143,700)	(122,400)	(414,300)	(359,600)
Operating Income/(Loss)	240,000	220,500	697,000	647,100
Interest Expense	(36,600)	(33,500)	(107,300)	(98,700)
Other Income, Net	10,100	5,000	28,300	17,300
Net Income/(Loss) Attributable to Common Shareholders	155,800	139,400	455,800	412,400
Cash Flows Used for Investments in Plant			823,300	691,000
Assets	13,225,300		13,225,300		12,377,800
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	65,100	61,800	168,200	161,000
Depreciation and Amortization	(12,700)	(11,500)	(37,500)	(34,300)
Other Operating Expenses	(28,800)	(26,100)	(82,900)	(76,700)
Operating Income/(Loss)	23,600	24,200	47,800	50,000
Interest Expense	(8,700)	(8,000)	(25,200)	(24,000)
Other Income, Net	2,100	1,200	6,400	3,100
Net Income/(Loss) Attributable to Common Shareholders	16,700	$ 17,500	29,400	30,000
Cash Flows Used for Investments in Plant			103,400	$ 91,200
Assets	$ 2,627,900		$ 2,627,900		$ 2,551,100