Consolidation - Revenue and Expenses of Consolidated Investment Product (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income:
Total revenues	$ 138,065	$ 152,210	$ 132,932	$ 129,028	$ 128,024	$ 123,675	$ 94,132	$ 79,776
Expenses:
Net Income (Loss) Attributable to Common Stockholders	$ 77	$ 24,913	$ 20,986	$ 21,216	$ 3,414	$ 16,708	$ (2,389)	$ 10,943	$ 67,192	$ 28,676	$ 48,502
CLOs
Income:
Realized and unrealized gain (loss), net									(16,202)
Interest Income									96,666
Total revenues									80,464
Expenses:
Other operating expenses									2,547
Interest expense									64,788
Total Expense									67,335
Noncontrolling interest									(37)
Net Income (Loss) Attributable to Common Stockholders									$ 13,092