CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Investments and receivables at fair value	$ 3,571.9	$ 3,408.5
Class A
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	172,152,979	171,463,760
Common stock, outstanding (in shares)	172,152,979	171,463,760
Class B
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	12,988,658	12,988,658
Common stock, outstanding (in shares)	12,988,658	12,988,658
Class C
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	190,031,873	198,153,613
Common stock, outstanding (in shares)	190,031,873	198,153,613