Variable Interest Entities - Summary of Assets and Liabilities of Consolidated CLO and Single Asset Securitization VIE (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Assets	$ 16,958,955	$ 16,551,871
Liabilities:
Liabilities	13,054,724	12,767,190
VIE [Member]
Assets:
Assets	3,587,950	1,401,691
Liabilities:
Liabilities	2,924,603	1,188,732
VIE [Member] | Loans Receivable [Member]
Assets:
Assets	3,520,130	1,349,903
Loans receivable, net	3,506,676	1,349,903
VIE [Member] | Current Expected Credit Loss Reserve [Member]
Assets:
Assets	(13,454)
VIE [Member] | Other Assets [Member]
Assets:
Assets	81,274	51,788
VIE [Member] | Securitized Debt Obligations, Net [Member]
Liabilities:
Liabilities	2,922,499	1,187,084
VIE [Member] | Other Liabilities [Member]
Liabilities:
Liabilities	$ 2,104	$ 1,648