Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financial assets
Cash and cash equivalents	$ 271,899	$ 551,154
Loans receivable, net	24,576,601	22,156,437
Debt securities held-to-maturity, net	0	79,200
Financial liabilities
Securitized debt obligations, net	2,844,032	2,838,062
Securitized debt obligations, net, Face Amount	2,855,625	2,855,625
Asset-specific debt net, Face Amount	959,762	400,699
Loan participations sold, net	207,225	0
Loan participations sold, net, Face Amount	207,762	0
Secured debt, net
Financial liabilities
Face Value	13,213,212	12,299,580
Secured term loans, net
Financial liabilities
Face Value	1,837,717	1,349,271
Senior secured notes, net
Financial liabilities
Face Value	400,000	400,000
Convertible notes, net
Financial liabilities
Face Value	520,000	622,500
Book Value
Financial assets
Cash and cash equivalents	271,899	551,154
Loans receivable, net	24,278,702	21,878,338
Debt securities held-to-maturity, net	0	78,013
Financial liabilities
Securitized debt obligations, net	2,844,032	2,838,062
Asset-specific debt, net	949,891	393,824
Loan participations sold, net	207,225	0
Book Value | Secured debt, net
Financial liabilities
Debt	13,188,692	12,280,042
Book Value | Secured term loans, net
Financial liabilities
Debt	1,807,017	1,327,406
Book Value | Senior secured notes, net
Financial liabilities
Debt	394,864	394,010
Book Value | Convertible notes, net
Financial liabilities
Debt	513,626	619,876
Fair Value
Financial assets
Cash and cash equivalents	271,899	551,154
Loans receivable, net	24,067,484	22,013,762
Debt securities held-to-maturity, net	0	77,229
Financial liabilities
Securitized debt obligations, net	2,785,573	2,850,399
Asset-specific debt, net	948,263	400,699
Loan participations sold, net	203,025	0
Fair Value | Secured debt, net
Financial liabilities
Debt	12,887,200	12,299,580
Fair Value | Secured term loans, net
Financial liabilities
Debt	1,746,369	1,335,844
Fair Value | Senior secured notes, net
Financial liabilities
Debt	340,008	399,012
Fair Value | Convertible notes, net
Financial liabilities
Debt	$ 477,134	$ 630,821