Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Deferred tax liabilities
Investments	$ (0.5)	$ (0.5)
Total deferred tax liabilities	(0.5)	(0.5)
Deferred tax assets
Deferred tax asset related to investments	514.5	278.2
Net operating loss carryforwards	68.1	46.2
Total deferred tax assets	582.6	324.4
Net deferred tax assets (liabilities)	$ 582.1	$ 323.9