Investments - Summary of Investments (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Total investments	$ 183.7	$ 184.7
Non Marketable Equity Securities
Schedule of Investments [Line Items]
Total investments	124.0	124.0
Seed Capital Investments
Schedule of Investments [Line Items]
Total investments	26.3	26.1
Marketable Equity Securities
Schedule of Investments [Line Items]
Total investments	22.5	23.1
Partnership Interests in Private Equity Funds
Schedule of Investments [Line Items]
Total investments	$ 10.9	$ 11.5