Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Accounting Policies [Abstract]
Accrued performance allocations and incentive fee-related compensation	$ 2,154.3		$ 2,154.3		$ 2,038.2
Percentage of estimated realizable tax benefit to be paid by corporate taxpayers on exchange transactions			85.00%
Securities transferred to counterparties under repurchase agreements	64.5		$ 64.5
Foreign currency transaction gain (loss)	$ (2.6)	$ 0.7	$ 18.9	$ (5.0)