Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before taxes		$ 1,064.4	$ 1,014.1	$ 1,364.8
Income tax benefit		(259.3)	(248.9)	(335.0)
Net income		805.1	765.2	$ 1,029.8
Unfunded Employee Benefit Obligations | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service costs	[1]	(5.1)	(4.8)
Amortization of actuarial gains / (losses)	[1]	(0.4)	(3.7)
Income before taxes		(5.5)	(8.5)
Income tax benefit		1.4	2.1
Net income		$ (4.1)	$ (6.4)

[1] These AOCI components are included in the computation of net pension and postretirement benefit costs. See Note 12, Employee Benefit Plans and Other Postretirement Benefits, for additional information.