Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ 5.2	$ (0.6)
Foreign Currency Exchange Forward Contracts | Operational currency exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	5.8	(0.3)
Foreign Currency Exchange Forward Contracts | Asset manager investment exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ (0.6)	$ (0.3)