Consolidation - Additional Information (Details)	6 Months Ended
	Jun. 30, 2020 USD ($) collateralized_loan_obligation	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
CLOs
Variable Interest Entity [Line Items]
Number of CLOs consolidated | collateralized_loan_obligation	6
Investments	$ 2,194,211,000		$ 1,976,148,000
Nonconsolidated VIEs
Variable Interest Entity [Line Items]
Carrying value and maximum risk of loss	$ 14,600,000
LIBOR | CLOs
Variable Interest Entity [Line Items]
Investments, basis spread on variable interest rate	8.50%
Senior Notes | CLOs
Variable Interest Entity [Line Items]
Unpaid principal balance exceeds fair value	$ 219,300,000
Subordinated Notes - Newfleet CLO 2016-1 | CLOs
Variable Interest Entity [Line Items]
Debt par value		$ 2,500,000,000
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		$ 2,300,000,000
Minimum | Senior Secured Floating Rate Notes - Newfleet CLO 2016-1 | LIBOR | CLOs
Variable Interest Entity [Line Items]
Basis spread on variable rate	0.80%
Maximum | Senior Secured Floating Rate Notes - Newfleet CLO 2016-1 | LIBOR | CLOs
Variable Interest Entity [Line Items]
Basis spread on variable rate	8.70%