Consolidation - Additional Information (Details)	6 Months Ended
	Jun. 30, 2021 USD ($) collateralizedLoanObligation	Dec. 31, 2020 USD ($)
Variable Interest Entity [Line Items]
Derivative assets	$ 0
Derivative liabilities	$ 0
CLOs
Variable Interest Entity [Line Items]
Number of CLOs consolidated | collateralizedLoanObligation	6
Investments	$ 2,154,956,000	$ 2,217,055,000
Nonconsolidated
Variable Interest Entity [Line Items]
Carrying value and maximum risk of loss	$ 30,800,000
LIBOR | CLOs
Variable Interest Entity [Line Items]
Investments, basis spread on variable interest rate (as percent)	10.00%
Senior Notes | CLOs
Variable Interest Entity [Line Items]
Unpaid principal balance exceeds fair value	$ 35,500,000
Subordinated Notes - Newfleet CLO 2016-1 | CLOs
Variable Interest Entity [Line Items]
Debt par value	2,300,000,000
Subordinated Notes - Newfleet CLO 2016-1 | Subordinated Debt | CLOs
Variable Interest Entity [Line Items]
Debt par value	225,900,000
Senior Secured Floating Rate Notes - Newfleet CLO 2016-1 | Senior Notes | CLOs
Variable Interest Entity [Line Items]
Debt par value	$ 2,100,000,000
Minimum | Senior Secured Floating Rate Notes - Newfleet CLO 2016-1 | LIBOR | CLOs
Variable Interest Entity [Line Items]
Basis spread on variable rate (as percent)	0.80%
Maximum | Senior Secured Floating Rate Notes - Newfleet CLO 2016-1 | LIBOR | CLOs
Variable Interest Entity [Line Items]
Basis spread on variable rate (as percent)	8.70%