Consolidated Income Statements - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Operating revenues	$ 9,597.4	$ 8,316.0	$ 7,241.7
Operating expenses
Cost of sales	4,358.9	3,311.0	2,319.5
Other operation and maintenance	1,938.0	2,005.5	2,032.2
Depreciation and amortization	1,122.6	1,074.3	975.9
Property and revenue taxes	253.7	210.3	208.0
Total operating expenses	7,673.2	6,601.1	5,535.6
Operating income	1,924.2	1,714.9	1,706.1
Equity in earnings of transmission affiliates	194.7	158.1	175.8
Other income, net	128.8	133.2	79.5
Interest expense	515.1	471.1	493.7
Loss on debt extinguishment	0.0	36.3	38.4
Other expense	(191.6)	(216.1)	(276.8)
Income before income taxes	1,732.6	1,498.8	1,429.3
Income tax expense	322.9	200.3	227.9
Net income	1,409.7	1,298.5	1,201.4
Preferred stock dividends of subsidiary	1.2	1.2	1.2
Net (income) loss attributed to noncontrolling interests	(0.4)	3.0	(0.3)
Net income attributed to common shareholders	$ 1,408.1	$ 1,300.3	$ 1,199.9
Earnings per share
Basic (in dollars per share)	$ 4.46	$ 4.12	$ 3.80
Diluted (in dollars per share)	$ 4.45	$ 4.11	$ 3.79
Weighted average common shares outstanding
Basic (in shares)	315.4	315.4	315.4
Diluted (in shares)	316.1	316.3	316.5