CONDENSED CONSOLIDATED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Operating revenues	$ 1,772.0	$ 1,830.0	$ 4,452.2	$ 4,718.1
Operating expenses
Cost of sales	469.7	533.0	1,396.8	1,842.7
Other operation and maintenance	533.4	496.0	1,064.2	1,030.0
Depreciation and amortization	336.6	313.9	670.0	619.4
Property and revenue taxes	67.5	61.8	143.0	131.4
Total operating expenses	1,407.2	1,404.7	3,274.0	3,623.5
Operating income	364.8	425.3	1,178.2	1,094.6
Equity in earnings of transmission affiliates	46.8	43.6	91.6	87.4
Other income, net	40.6	48.3	84.7	89.1
Interest expense	200.6	178.7	392.6	350.9
Other expense	(113.2)	(86.8)	(216.3)	(174.4)
Income before income taxes	251.6	338.5	961.9	920.2
Income tax expense	41.6	48.5	129.3	122.6
Net income	210.0	290.0	832.6	797.6
Preferred stock dividends of subsidiary	0.3	0.3	0.6	0.6
Net loss attributed to noncontrolling interests	1.6	0.0	1.6	0.2
Net income attributed to common shareholders	$ 211.3	$ 289.7	$ 833.6	$ 797.2
Earnings per share
Basic (in dollars per share)	$ 0.67	$ 0.92	$ 2.64	$ 2.53
Diluted (in dollars per share)	$ 0.67	$ 0.92	$ 2.64	$ 2.52
Weighted average common shares outstanding
Basic (in shares)	315.9	315.4	315.8	315.4
Diluted (in shares)	316.2	315.9	316.1	315.9