Schedule IV - Mortgage Loans on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 817,477
Face amount of loans	19,203,126
Carrying amount of loans	19,047,518	$ 23,787,012	$ 25,017,880	$ 22,003,017
Principal Amount of Loans Subject to Delinquent Principal or Interest	525,699
CECL reserve	(733,936)	(576,936)	(326,137)
Total Loans, Net	18,313,582	23,210,076	24,691,743
Charge-offs	(384,603)	$ 0	$ 0
First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	18,859,609
Carrying amount of loans	18,726,484
Principal Amount of Loans Subject to Delinquent Principal or Interest	525,699
Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	15,851,006
Carrying amount of loans	15,728,609
Principal Amount of Loans Subject to Delinquent Principal or Interest	525,699
Subordinated Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	817,477
Face amount of loans	343,515
Carrying amount of loans	321,034
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 525,699
Office | First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.17%
Prior Liens	$ 0
Face amount of loans	1,329,829
Carrying amount of loans	1,327,886
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Office | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	4,658,555
Carrying amount of loans	4,607,433
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 330,699
Interest Payment Rates, Fixed	6.00%
Mixed Use | First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.20%
Prior Liens	$ 0
Face amount of loans	860,102
Carrying amount of loans	855,764
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Mixed Use | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	1,860,795
Carrying amount of loans	1,847,567
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Hospitality | First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.75%
Prior Liens	$ 0
Face amount of loans	818,672
Carrying amount of loans	814,225
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Hospitality | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	1,893,271
Carrying amount of loans	1,854,663
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Multifamily | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	4,960,975
Carrying amount of loans	4,947,380
Principal Amount of Loans Subject to Delinquent Principal or Interest	195,000
Industrial | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	1,380,784
Carrying amount of loans	1,376,442
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Other | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	472,118
Carrying amount of loans	471,427
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Retail | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	335,784
Carrying amount of loans	335,213
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Life Sciences / Studio | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	288,724
Carrying amount of loans	288,484
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Various | Subordinated Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	817,477
Face amount of loans	343,515
Carrying amount of loans	321,034
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Minimum | Office | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rate, subject to floor	(1.30%)
Minimum | Mixed Use | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.76%
Minimum | Hospitality | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.11%
Minimum | Multifamily | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	1.71%
Minimum | Industrial | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.71%
Minimum | Other | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.25%
Minimum | Retail | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.95%
Minimum | Life Sciences / Studio | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.66%
Minimum | Various | Subordinated Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.70%
Maximum | Office | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rate, subject to floor	4.62%
Maximum | Mixed Use | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.60%
Maximum | Hospitality | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.95%
Maximum | Multifamily | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	8.86%
Maximum | Industrial | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.60%
Maximum | Other | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.11%
Maximum | Retail | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.33%
Maximum | Life Sciences / Studio | Second Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.75%
Maximum | Various | Subordinated Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.75%