Summary of Significant Accounting Policies - Principles of Consolidation (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Consolidated VIEs, assets	$ 21,403.0	$ 21,250.4	$ 15,644.8
Consolidated VIEs, liabilities	14,581.7	15,544.2
Investment fund	374.6
Collateralized Loan Obligations
Variable Interest Entity [Line Items]
Investment in CLOs	110.6
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Consolidated VIEs, assets	7,200.0	6,900.0
Consolidated VIEs, liabilities	$ 6,200.0	$ 6,600.0