Fair Values - Schedule of Details of Book Value, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financial assets
Cash and cash equivalents	$ 413,986	$ 350,014
Loans receivable, net	23,317,882	23,923,719
Financial liabilities
Securitized debt obligations, net	2,328,073	2,505,417
Securitized debt obligations, net, Face Amount	2,329,456	2,507,514
Asset-specific debt net, Face Amount	1,064,484	1,004,097
Loan participations sold, net	334,909	337,179
Loan participations sold, net, Face Amount	335,280	337,721
Secured debt, net
Financial liabilities
Debt, Face Amount	12,403,449	12,697,058
Secured term loans, net
Financial liabilities
Debt, Face Amount	2,129,723	2,135,221
Senior secured notes, net
Financial liabilities
Debt, Face Amount	339,918	366,090
Convertible notes, net
Financial liabilities
Debt, Face Amount	300,000	300,000
Book Value
Financial assets
Cash and cash equivalents	413,986	350,014
Loans receivable, net	22,437,942	23,210,076
Financial liabilities
Securitized debt obligations, net	2,328,073	2,505,417
Asset-specific debt, net	1,061,380	1,000,210
Loan participations sold, net	334,909	337,179
Book Value | Secured debt, net
Financial liabilities
Debt	12,387,289	12,683,095
Book Value | Secured term loans, net
Financial liabilities
Debt	2,098,415	2,101,632
Book Value | Senior secured notes, net
Financial liabilities
Debt	337,083	362,763
Book Value | Convertible notes, net
Financial liabilities
Debt	296,166	295,847
Fair Value
Financial assets
Cash and cash equivalents	413,986	350,014
Loans receivable, net	22,275,189	23,015,737
Financial liabilities
Securitized debt obligations, net	2,161,784	2,323,441
Asset-specific debt, net	1,051,739	992,357
Loan participations sold, net	331,626	333,745
Fair Value | Secured debt, net
Financial liabilities
Debt	12,162,645	12,425,609
Fair Value | Secured term loans, net
Financial liabilities
Debt	2,102,411	2,102,950
Fair Value | Senior secured notes, net
Financial liabilities
Debt	302,283	327,081
Fair Value | Convertible notes, net
Financial liabilities
Debt	$ 273,521	$ 272,076