CONDENSED CONSOLIDATED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Operating revenues	$ 1,863.5	$ 1,957.4	$ 6,315.7	$ 6,675.5
Operating expenses
Cost of sales	520.8	587.4	1,917.6	2,430.1
Other operation and maintenance	566.8	516.6	1,631.0	1,546.6
Depreciation and amortization	340.5	320.3	1,010.5	939.7
Property and revenue taxes	51.7	61.1	194.7	192.5
Total operating expenses	1,479.8	1,485.4	4,753.8	5,108.9
Operating income	383.7	472.0	1,561.9	1,566.6
Equity in earnings of transmission affiliates	46.7	44.7	138.3	132.1
Other income, net	44.0	41.8	128.7	130.9
Interest expense	204.2	182.5	596.8	533.4
Other expense	(113.5)	(96.0)	(329.8)	(270.4)
Income before income taxes	270.2	376.0	1,232.1	1,296.2
Income tax expense	31.6	60.4	160.9	183.0
Net income	238.6	315.6	1,071.2	1,113.2
Preferred stock dividends of subsidiary	0.3	0.3	0.9	0.9
Net loss attributed to noncontrolling interests	1.8	0.7	3.4	0.9
Net income attributed to common shareholders	$ 240.1	$ 316.0	$ 1,073.7	$ 1,113.2
Earnings per share
Basic (in dollars per share)	$ 0.76	$ 1.00	$ 3.40	$ 3.53
Diluted (in dollars per share)	$ 0.76	$ 1.00	$ 3.40	$ 3.52
Weighted average common shares outstanding
Basic (in shares)	316.2	315.4	315.9	315.4
Diluted (in shares)	316.5	315.8	316.2	315.9