Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ (0.6)	$ 0.9
Operational currency exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	(0.3)	0.4
Asset manager investment exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	(0.3)	(0.2)
Total return strategy
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ 0.0	$ 0.7