Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Notional Amount	$ 151.0	$ 164.5
Derivative assets (liabilities), at fair value, net	2.7	1.3
Operational currency exposure
Schedule of Investments [Line Items]
Notional Amount	0.0	75.4
Derivative assets (liabilities), at fair value, net	0.0	1.8
Asset manager investment exposure
Schedule of Investments [Line Items]
Notional Amount	151.0	89.1
Derivative assets (liabilities), at fair value, net	$ 2.7	$ (0.5)