CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Other Comprehensive Income [Abstract]
Net income	$ 210.0	$ 290.0	$ 832.6	$ 797.6
Derivatives accounted for as cash flow hedges
Reclassification of realized derivative gains to net income, net of tax	0.0	0.0	(0.1)	(0.1)
Comprehensive income	210.0	290.0	832.5	797.5
Preferred stock dividends of subsidiary	0.3	0.3	0.6	0.6
Comprehensive loss attributed to noncontrolling interests	1.6	0.0	1.6	0.2
Comprehensive income attributed to common shareholders	$ 211.3	$ 289.7	$ 833.5	$ 797.1