SEGMENT INFORMATION - Schedule of Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 12,289,336	$ 9,863,085	$ 8,904,430
Depreciation and Amortization	(1,643,100)	(1,335,000)	(1,159,100)
Other Operating Expenses	(8,448,000)	(6,534,800)	(5,756,600)
Operating Income	2,198,154	1,993,321	1,988,734
Interest Expense	(678,274)	(582,334)	(538,452)
Interest Income	50,500	25,600	4,800
Other Income, Net	295,600	135,700	103,800
Income Tax (Expense)/Benefit	(453,574)	(344,223)	(346,186)
Net Income	1,412,394	1,228,046	1,212,686
Net Income Attributable to Noncontrolling Interests	(7,519)	(7,519)	(7,519)
Net Income Attributable to Common Shareholders	1,404,875	1,220,527	1,205,167
Total Assets (as of)	53,230,900	48,492,144
Cash Flows Used for Investments in Plant	3,441,852	3,175,080	2,942,996
Operating Segments | Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues	9,405,300	7,423,600	7,132,300
Depreciation and Amortization	(970,400)	(737,800)	(657,000)
Other Operating Expenses	(7,663,700)	(5,970,000)	(5,642,300)
Operating Income	771,200	715,800	833,000
Interest Expense	(253,100)	(236,400)	(216,000)
Interest Income	45,100	20,700	3,200
Other Income, Net	180,400	78,100	58,000
Income Tax (Expense)/Benefit	(146,200)	(103,500)	(129,600)
Net Income	597,400	474,700	548,600
Net Income Attributable to Noncontrolling Interests	(4,600)	(4,600)	(4,600)
Net Income Attributable to Common Shareholders	592,800	470,100	544,000
Total Assets (as of)	27,365,000	25,411,200
Cash Flows Used for Investments in Plant	1,172,600	1,053,300	1,079,000
Operating Segments | Natural Gas Distribution
Segment Reporting Information [Line Items]
Operating Revenues	2,215,600	1,789,600	1,208,700
Depreciation and Amortization	(157,600)	(142,300)	(87,900)
Other Operating Expenses	(1,727,000)	(1,345,400)	(913,800)
Operating Income	331,000	301,900	207,000
Interest Expense	(71,400)	(58,600)	(40,000)
Interest Income	10,200	4,500	900
Other Income, Net	33,600	17,900	3,100
Income Tax (Expense)/Benefit	(69,200)	(60,900)	(36,900)
Net Income	234,200	204,800	134,100
Net Income Attributable to Noncontrolling Interests	0	0	0
Net Income Attributable to Common Shareholders	234,200	204,800	134,100
Total Assets (as of)	8,084,900	7,215,900
Cash Flows Used for Investments in Plant	710,300	721,100	494,400
Operating Segments | Electric Transmission
Segment Reporting Information [Line Items]
Operating Revenues	1,808,700	1,634,600	1,536,100
Depreciation and Amortization	(337,400)	(300,300)	(278,100)
Other Operating Expenses	(548,400)	(496,200)	(470,000)
Operating Income	922,900	838,100	788,000
Interest Expense	(145,500)	(133,200)	(126,800)
Interest Income	500	2,200	4,700
Other Income, Net	37,900	19,800	23,300
Income Tax (Expense)/Benefit	(216,300)	(179,400)	(183,800)
Net Income	599,500	547,500	505,400
Net Income Attributable to Noncontrolling Interests	(2,900)	(2,900)	(2,900)
Net Income Attributable to Common Shareholders	596,600	544,600	502,500
Total Assets (as of)	13,369,500	12,377,800
Cash Flows Used for Investments in Plant	1,144,000	1,024,100	1,004,600
Operating Segments | Water Distribution
Segment Reporting Information [Line Items]
Operating Revenues	222,500	211,300	215,400
Depreciation and Amortization	(50,900)	(46,100)	(44,200)
Other Operating Expenses	(111,800)	(101,400)	(86,600)
Operating Income	59,800	63,800	84,600
Interest Expense	(34,700)	(32,000)	(32,900)
Interest Income	0	0	0
Other Income, Net	8,500	3,300	2,000
Income Tax (Expense)/Benefit	3,200	1,700	(12,500)
Net Income	36,800	36,800	41,200
Net Income Attributable to Noncontrolling Interests	0	0	0
Net Income Attributable to Common Shareholders	36,800	36,800	41,200
Total Assets (as of)	2,783,800	2,551,100
Cash Flows Used for Investments in Plant	154,400	137,200	118,800
Other
Segment Reporting Information [Line Items]
Operating Revenues	1,435,500	1,354,000	1,235,900
Depreciation and Amortization	(132,600)	(113,100)	(93,500)
Other Operating Expenses	(1,189,100)	(1,170,400)	(1,071,900)
Operating Income	113,800	70,500	70,500
Interest Expense	(247,800)	(168,800)	(161,000)
Interest Income	66,300	46,000	37,800
Other Income, Net	1,600,800	1,363,900	1,382,900
Income Tax (Expense)/Benefit	(25,100)	(2,100)	16,600
Net Income	1,508,000	1,309,500	1,346,800
Net Income Attributable to Noncontrolling Interests	0	0	0
Net Income Attributable to Common Shareholders	1,508,000	1,309,500	1,346,800
Total Assets (as of)	26,365,200	22,674,700
Cash Flows Used for Investments in Plant	260,600	239,400	246,200
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(2,798,300)	(2,550,000)	(2,424,000)
Depreciation and Amortization	5,800	4,600	1,600
Other Operating Expenses	2,792,000	2,548,600	2,428,000
Operating Income	(500)	3,200	5,600
Interest Expense	74,200	46,600	38,300
Interest Income	(71,600)	(47,800)	(41,800)
Other Income, Net	(1,565,600)	(1,347,300)	(1,365,500)
Income Tax (Expense)/Benefit	0	0	0
Net Income	(1,563,500)	(1,345,300)	(1,363,400)
Net Income Attributable to Noncontrolling Interests	0	0	0
Net Income Attributable to Common Shareholders	(1,563,500)	(1,345,300)	(1,363,400)
Total Assets (as of)	(24,737,500)	(21,738,600)
Cash Flows Used for Investments in Plant	$ 0	$ 0	$ 0