CONDENSED INCOME STATEMENTS - USD ($) $ 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	$ 337.0	$ 381.0	$ 764.2	$ 872.5
Operating expenses
Cost of sales	89.7	117.8	244.6	345.2
Other operation and maintenance	111.3	105.4	215.9	213.3
Depreciation and amortization	59.2	56.2	118.3	111.2
Property and revenue taxes	11.5	11.7	23.5	23.9
Total operating expenses	271.7	291.1	602.3	693.6
Operating income	65.3	89.9	161.9	178.9
Other income, net	12.5	12.7	24.0	24.4
Interest expense	23.9	22.2	47.9	44.0
Other expense	(11.4)	(9.5)	(23.9)	(19.6)
Income before income taxes	53.9	80.4	138.0	159.3
Income tax expense	10.2	16.3	26.9	28.9
Net income	$ 43.7	$ 64.1	$ 111.1	$ 130.4