Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial assets
Cash and cash equivalents	$ 309,425	$ 551,154
Loans receivable, net	23,873,563	22,156,437
Debt securities held-to-maturity, net	0	79,200
Financial liabilities
Securitized debt obligations, net	2,839,818	2,838,062
Securitized debt obligations, net, Face Amount	2,855,625	2,855,625
Asset-specific debt net, Face Amount	469,766	400,699
Loan participations sold, net	243,760	0
Loan participations sold, net, Face Amount	244,367	0
Secured debt, net
Financial liabilities
Face Value	13,117,249	12,299,580
Secured term loans, net
Financial liabilities
Face Value	1,345,837	1,349,271
Senior secured notes, net
Financial liabilities
Face Value	400,000	400,000
Convertible notes, net
Financial liabilities
Face Value	857,850	622,500
Book Value
Financial assets
Cash and cash equivalents	309,425	551,154
Loans receivable, net	23,586,769	21,878,338
Debt securities held-to-maturity, net	0	78,013
Financial liabilities
Securitized debt obligations, net	2,839,818	2,838,062
Asset-specific debt, net	463,097	393,824
Loan participations sold, net	243,760	0
Book Value | Secured debt, net
Financial liabilities
Debt	13,092,408	12,280,042
Book Value | Secured term loans, net
Financial liabilities
Debt	1,325,222	1,327,406
Book Value | Senior secured notes, net
Financial liabilities
Debt	394,303	394,010
Book Value | Convertible notes, net
Financial liabilities
Debt	850,084	619,876
Fair Value
Financial assets
Cash and cash equivalents	309,425	551,154
Loans receivable, net	23,684,237	22,013,762
Debt securities held-to-maturity, net	0	77,229
Financial liabilities
Securitized debt obligations, net	2,825,774	2,850,399
Asset-specific debt, net	469,766	400,699
Loan participations sold, net	244,367	0
Fair Value | Secured debt, net
Financial liabilities
Debt	13,117,249	12,299,580
Fair Value | Secured term loans, net
Financial liabilities
Debt	1,333,424	1,335,844
Fair Value | Senior secured notes, net
Financial liabilities
Debt	373,112	399,012
Fair Value | Convertible notes, net
Financial liabilities
Debt	$ 858,042	$ 630,821