Investments - Schedule of Realized and Unrealized Gains and Losses on Investments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Unrealized gains on equity securities held as of the end of the period	$ 2.9	$ 25.8	$ 6.5
Realized gains (losses) for equity securities sold during the period	0.7	(1.1)	10.9
Total gains recognized in other income (expense), net	$ 3.6	$ 24.7	$ 17.4