Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial assets
Cash and cash equivalents	$ 355,018	$ 150,090
Loans receivable, net	16,468,767	16,277,343
Debt securities held-to-maturity	84,244	88,958
Financial liabilities
Secured debt agreements, net, face amount	9,367,270	10,083,938
Securitized debt obligations, net	2,239,640	1,187,084
Securitized debt obligations, net,face amount	2,253,008	1,189,642
Secured term loan, net	745,006	746,878
Book Value [Member]
Financial assets
Cash and cash equivalents	355,018	150,090
Loans receivable, net	16,250,914	16,164,801
Debt securities held-to-maturity	76,936	86,638
Financial liabilities
Secured debt agreements, net	9,335,709	10,054,930
Securitized debt obligations, net	2,239,640	1,187,084
Secured term loan, net	734,695	736,142
Convertible notes, net	613,882	613,071
Fair Value [Member]
Financial assets
Cash and cash equivalents	355,018	150,090
Loans receivable, net	16,316,003	16,279,904
Debt securities held-to-maturity	73,656	88,305
Financial liabilities
Secured debt agreements, net	9,367,270	10,083,938
Securitized debt obligations, net	1,993,068	1,189,368
Secured term loan, net	640,705	750,769
Convertible notes, net	490,378	665,900
Convertible Senior Note [Member]
Financial liabilities
Convertible notes, net, face amount	$ 622,500	$ 622,500