Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets
Cash and cash equivalents	$ 150,090	$ 105,662
Loans receivable, net	16,277,343	14,293,970
Debt securities held-to-maturity	88,958	99,000
Financial liabilities
Secured debt agreements, net, face amount	10,083,938	8,996,481
Loan participations sold, net	0	94,418
Loan participations sold, net, face amount		123,745
Securitized debt obligations, net	1,187,084	1,285,471
Securitized debt obligations, net,face amount	1,189,642	1,292,120
Secured term loan, net	746,878
Book Value [Member]
Financial assets
Cash and cash equivalents	150,090	105,662
Loans receivable, net	16,164,801	14,191,200
Debt securities held-to-maturity	86,638	96,167
Financial liabilities
Secured debt agreements, net	10,054,930	8,974,756
Loan participations sold, net		94,418
Securitized debt obligations, net	1,187,084	1,285,471
Secured term loan, net	736,142
Convertible notes, net	613,071	609,911
Fair Value [Member]
Financial assets
Cash and cash equivalents	150,090	105,662
Loans receivable, net	16,279,904	14,294,836
Debt securities held-to-maturity	88,305	96,600
Financial liabilities
Secured debt agreements, net	10,083,938	8,996,481
Loan participations sold, net		94,528
Securitized debt obligations, net	1,189,368	1,283,086
Secured term loan, net	750,769
Convertible notes, net	665,900	605,348
Convertible Senior Note [Member]
Financial liabilities
Convertible notes, net, face amount	$ 622,500	622,500
Senior Participation [Member]
Financial liabilities
Loan participations sold, net		94,418
Loan participations sold, net, face amount		$ 94,528