Investments - Summary of Investments (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Total investments	$ 160.1	$ 172.8
Non Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Total investments	84.5	84.5
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Total investments	26.8	40.8
Seed Capital Investments [Member]
Schedule of Investments [Line Items]
Total investments	34.0	32.0
Partnership Interests in Private Equity Funds [Member]
Schedule of Investments [Line Items]
Total investments	$ 14.8	$ 15.5