Accumulated Other Comprehensive Income (Loss) - Summary of Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Actuarial losses	$ (5.5)	$ (1.8)
Tax expense	(1.8)	(8.1)
Net income	12.5	37.4
Reclassification Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Total before tax	0.4	0.4
Tax expense	(0.1)	(0.1)
Net income	0.3	0.3
Reclassification Out of Accumulated Other Comprehensive Income | Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Actuarial losses	$ 0.4	$ 0.4