Variable Interest Entities - Summary of Assets and Liabilities of Consolidated CLO and Single Asset Securitization VIE (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Assets	$ 17,663,123	$ 16,551,871
Liabilities:
Liabilities	13,767,339	12,767,190
VIE [Member]
Assets:
Assets	2,709,080	1,401,691
Liabilities:
Liabilities	2,242,139	1,188,732
VIE [Member] | Loans Receivable [Member]
Assets:
Assets	2,644,344	1,349,903
Loans receivable, net	2,629,528	1,349,903
VIE [Member] | Current Expected Credit Loss Reserve [Member]
Assets:
Assets	(14,816)
VIE [Member] | Other Assets [Member]
Assets:
Assets	79,552	51,788
VIE [Member] | Securitized Debt Obligations, Net [Member]
Liabilities:
Liabilities	2,240,612	1,187,084
VIE [Member] | Other Liabilities [Member]
Liabilities:
Liabilities	$ 1,527	$ 1,648