Consolidation - Revenue and Expenses of Consolidated Investment Product (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income:
Total Income	$ 171,646	$ 154,790	$ 132,894	$ 144,566	$ 146,084	$ 145,955	$ 140,489	$ 130,718
Expenses:
Net Income (Loss) Attributable to Common Stockholders	$ 43,315	$ 29,648	$ 11,279	$ (4,285)	$ 20,808	$ 22,000	$ 24,842	$ 19,662	$ 79,957	$ 87,312	$ 67,192
CLOs
Income:
Realized and unrealized gain (loss), net									(6,519)
Interest income									106,536
Total Income									100,017
Expenses:
Other operating expenses									9,991
Interest expense									85,437
Total Expense									95,428
Noncontrolling interests									(1,298)
Net Income (Loss) Attributable to Common Stockholders									$ 3,291