CONDENSED CONSOLIDATED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Operating revenues	$ 1,957.4	$ 2,003.0	$ 6,675.5	$ 7,039.0
Operating expenses
Cost of sales	587.4	805.1	2,430.1	3,123.5
Other operation and maintenance	516.6	454.3	1,546.6	1,357.7
Depreciation and amortization	320.3	280.3	939.7	838.0
Property and revenue taxes	61.1	59.1	192.5	176.0
Total operating expenses	1,485.4	1,598.8	5,108.9	5,495.2
Operating income	472.0	404.2	1,566.6	1,543.8
Equity in earnings of transmission affiliates	44.7	63.7	132.1	148.4
Other income, net	41.8	34.7	130.9	94.1
Interest expense	182.5	127.5	533.4	364.9
Other expense	(96.0)	(29.1)	(270.4)	(122.4)
Income before income taxes	376.0	375.1	1,296.2	1,421.4
Income tax expense	60.4	73.4	183.0	263.9
Net income	315.6	301.7	1,113.2	1,157.5
Preferred stock dividends of subsidiary	0.3	0.3	0.9	0.9
Net loss (income) attributed to noncontrolling interests	0.7	0.6	0.9	(1.2)
Net income attributed to common shareholders	$ 316.0	$ 302.0	$ 1,113.2	$ 1,155.4
Earnings per share
Basic (in dollars per share)	$ 1.00	$ 0.96	$ 3.53	$ 3.66
Diluted (in dollars per share)	$ 1.00	$ 0.96	$ 3.52	$ 3.65
Weighted average common shares outstanding
Basic (in shares)	315.4	315.4	315.4	315.4
Diluted (in shares)	315.8	316.2	315.9	316.2