Variable Interest Entities - Summary of Assets and Liabilities of Consolidated CLO and Single Asset Securitization VIE (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Assets	$ 1,500,000	$ 1,500,000
VIE [Member]
Assets:
Assets	1,504,461	1,505,440
Liabilities:
Liabilities	1,290,191	1,287,626
VIE [Member] | Loans Receivable [Member]
Assets:
Assets	1,446,375	1,500,000
VIE [Member] | Other Assets [Member]
Assets:
Assets	58,086	5,440
VIE [Member] | Securitized Debt Obligations, Net [Member]
Liabilities:
Liabilities	1,288,389	1,285,471
VIE [Member] | Other Liabilities [Member]
Liabilities:
Liabilities	$ 1,802	$ 2,155