Variable Interest Entities - Additional Information - (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Variable Interest Entity [Line Items]
Held to maturity security	$ 8,557,000		$ 8,487,000
Income from investment in CLO warehouse entities	2,226,000	$ 3,184,000
Collateralized Loan Obligation Funds
Variable Interest Entity [Line Items]
Held to maturity security	8,557,000		8,487,000
Income from investment in CLO warehouse entities	2,226,000	3,184,000
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	$ 1,717,000	$ 6,574,000

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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