Summary of Significant Accounting Policies - Reconciliation between Basic and Diluted Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Net income	$ 870.5	$ 671.8	$ 587.1
Net income attributable to unvested awarded performance stock	(13.3)	(12.7)	(12.9)
Net income attributable to common shares	$ 857.2	$ 659.1	$ 574.2
Weighted average number of common shares outstanding – basic	283.9	282.9	282.2
Less unvested awarded performance stock included in weighted average number of common shares outstanding – basic	(4.3)	(5.4)	(6.2)
Weighted average number of common shares outstanding for basic earnings per common share	279.6	277.5	276.0
Dilutive effect of stock options	1.2	1.1	1.4
Weighted average number of shares outstanding – diluted	280.8	278.6	277.4
Net income per share:
Basic (in dollars per share)	$ 3.07	$ 2.38	$ 2.08
Diluted (in dollars per share)	$ 3.05	$ 2.37	$ 2.07