Investments - Summary of Investments (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Total investments	$ 192.9	$ 193.9
Non Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Total investments	124.0	124.0
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Total investments	24.4	24.3
Seed Capital Investments [Member]
Schedule of Investments [Line Items]
Total investments	31.3	30.6
Partnership Interests in Private Equity Funds [Member]
Schedule of Investments [Line Items]
Total investments	$ 13.2	$ 15.0