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Variable Interest Entities - Additional Information - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Held to maturity security				$ 8,403	$ 8,557
Income from investment in CLO warehouse entities			$ 1,954
Collateralized Loan Obligation Funds
Variable Interest Entity [Line Items]
Held to maturity security				8,403	8,557
Income from investment in CLO warehouse entities	$ 0		1,954
Collateralized Loan Obligation Funds \| Warehouse CLO Funds
Variable Interest Entity [Line Items]
Equity investments				$ 0	$ 0
Asset management fees
Variable Interest Entity [Line Items]
Asset management fees		$ 1,717	$ 1,717