Summary of Impact of Derivative Financial Instruments to Consolidated Statements of Operations (Detail) - Freestanding Derivatives - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Realized Gains (Losses)	$ 4,544	$ 13,215	$ (12,619)
Net Change in Unrealized Gain (Loss)	54,650	27,162	(23,622)
Total Return Swaps
Derivative [Line Items]
Realized Gains (Losses)	(908)	145	295
Net Change in Unrealized Gain (Loss)	1,296	(2,107)	(447)
Credit Default Swap
Derivative [Line Items]
Realized Gains (Losses)	3,209	(539)	(3,764)
Net Change in Unrealized Gain (Loss)	3,400	(521)	4,881
Interest Rate Contracts
Derivative [Line Items]
Realized Gains (Losses)	(3,570)	2,968	(2,400)
Net Change in Unrealized Gain (Loss)	50,431	36,472	(24,629)
Foreign Currency Contracts
Derivative [Line Items]
Realized Gains (Losses)	6,099	10,761	(6,333)
Net Change in Unrealized Gain (Loss)	(441)	(6,682)	(3,556)
Other
Derivative [Line Items]
Realized Gains (Losses)	(286)	$ (120)	(417)
Net Change in Unrealized Gain (Loss)	$ (36)		$ 129