Schedule IV - Mortgage Loans on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 1,148,233
Face amount of loans	23,923,719
Carrying amount of loans	23,787,012	$ 25,017,880	$ 22,003,017	$ 16,572,715
Principal Amount of Loans Subject to Delinquent Principal or Interest	140,000
CECL reserve	(576,936)	(326,137)	(124,679)
Total Loans, Net	23,210,076	24,691,743	21,878,338
Principal charge-offs	0	$ 0	$ (14,427)
Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	20,576,834
Carrying amount of loans	20,454,705
Principal Amount of Loans Subject to Delinquent Principal or Interest	140,000
Senior Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	23,634,365
Carrying amount of loans	23,499,645
Principal Amount of Loans Subject to Delinquent Principal or Interest	140,000
Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,148,233
Face amount of loans	289,354
Carrying amount of loans	287,367
Principal Amount of Loans Subject to Delinquent Principal or Interest	140,000
Office | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	6,507,693
Carrying amount of loans	6,455,942
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Mixed Use | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	1,864,832
Carrying amount of loans	1,855,982
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 140,000
Hospitality | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates, Fixed	7.90%
Prior Liens	$ 0
Face amount of loans	3,230,471
Carrying amount of loans	3,205,185
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Multifamily | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates, Fixed	1.50%
Prior Liens	$ 0
Face amount of loans	5,882,506
Carrying amount of loans	5,859,896
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Industrial | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	1,647,704
Carrying amount of loans	1,637,876
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Other | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	641,703
Carrying amount of loans	640,913
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Retail | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	458,495
Carrying amount of loans	456,993
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Life Sciences / Studio | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face amount of loans	343,430
Carrying amount of loans	341,918
Principal Amount of Loans Subject to Delinquent Principal or Interest	0
Various | Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,148,233
Face amount of loans	289,354
Carrying amount of loans	287,367
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
New York | Office | Borrower A | Senior loans in excess of 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.29%
Prior Liens	$ 0
Face amount of loans	1,156,396
Carrying amount of loans	1,154,771
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Ireland | Mixed Use | Borrower B | Senior loans in excess of 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.03%
Prior Liens	$ 0
Face amount of loans	999,907
Carrying amount of loans	995,570
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Australia | Hospitality | Borrower C | Senior loans in excess of 3% of the carrying amount of total loans
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	901,228
Carrying amount of loans	894,599
Principal Amount of Loans Subject to Delinquent Principal or Interest	$ 0
Minimum | Office | Senior loans less than 3% of the carrying amount of total loans
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 | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.76%
Minimum | Hospitality | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.31%
Minimum | Multifamily | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	1.71%
Minimum | Industrial | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.71%
Minimum | Other | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.25%
Minimum | Retail | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.36%
Minimum | Life Sciences / Studio | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.87%
Minimum | Various | Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.22%
Maximum | Office | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rate, subject to floor	10.50%
Maximum | Mixed Use | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.60%
Maximum | Hospitality | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	6.07%
Maximum | Multifamily | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.45%
Maximum | Industrial | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.60%
Maximum | Other | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.04%
Maximum | Retail | Senior loans less than 3% of the carrying amount of total loans
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 | Senior loans less than 3% of the carrying amount of total loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.50%
Maximum | Various | Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.50%