CONDENSED CONSOLIDATED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Operating revenues	$ 1,830.0	$ 2,127.9	$ 4,718.1	$ 5,036.0
Operating expenses
Cost of sales	533.0	935.0	1,842.7	2,318.4
Other operation and maintenance	496.0	449.0	1,030.0	903.4
Depreciation and amortization	313.9	279.6	619.4	557.7
Property and revenue taxes	61.8	56.1	131.4	116.9
Total operating expenses	1,404.7	1,719.7	3,623.5	3,896.4
Operating income	425.3	408.2	1,094.6	1,139.6
Equity in earnings of transmission affiliates	43.6	43.0	87.4	84.7
Other income, net	48.3	19.8	89.1	59.4
Interest expense	178.7	119.8	350.9	237.4
Other expense	(86.8)	(57.0)	(174.4)	(93.3)
Income before income taxes	338.5	351.2	920.2	1,046.3
Income tax expense	48.5	63.4	122.6	190.5
Net income	290.0	287.8	797.6	855.8
Preferred stock dividends of subsidiary	0.3	0.3	0.6	0.6
Net loss (income) attributed to noncontrolling interests	0.0	0.0	0.2	(1.8)
Net income attributed to common shareholders	$ 289.7	$ 287.5	$ 797.2	$ 853.4
Earnings per share
Basic (in dollars per share)	$ 0.92	$ 0.91	$ 2.53	$ 2.71
Diluted (in dollars per share)	$ 0.92	$ 0.91	$ 2.52	$ 2.70
Weighted average common shares outstanding
Basic (in shares)	315.4	315.4	315.4	315.4
Diluted (in shares)	315.9	316.2	315.9	316.2