Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax liabilities
Investments	$ (0.5)	$ (0.4)
Total deferred tax liabilities	(0.5)	(0.4)
Deferred tax assets
Deferred tax asset related to investments	148.9	102.3
Net operating loss carryforwards	28.3	15.0
Total deferred tax assets	177.2	117.3
Net deferred tax assets (liabilities)	$ 176.7	$ 116.9