Schedule IV - Mortgage Loans on Real Estate (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 1,649,939,000
Face amount of loans	25,160,343,000
Carrying amount of loans	25,017,880,000	$ 22,003,017,000	$ 16,572,715,000	$ 16,164,801,000
CECL reserve	(326,137,000)	(124,679,000)	(173,549,000)
Total Loans, Net	24,691,743,000	21,878,338,000	16,399,166,000
Loan fundings	6,810,218,000	12,550,463,000	1,896,276,000
Amortization of fees and other items	80,632,000	68,267,000	56,279,000
Loan repayments and sales proceeds	(3,168,155,000)	(6,733,105,000)	(1,862,955,000)
Unrealized (loss) gain on foreign currency translation	(632,902,000)	(297,894,000)	340,260,000
Deferred fees and other items	(74,930,000)	$ (143,002,000)	$ (21,946,000)
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	21,927,352,000
Carrying amount of loans	21,808,563,000
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	24,767,353,000
Carrying amount of loans	24,628,933,000
Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,649,939,000
Face amount of loans	392,990,000
Carrying amount of loans	388,947,000
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	1,811,126,000
Carrying amount of loans	1,801,511,000
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	6,924,092,000
Carrying amount of loans	6,893,477,000
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]
Prior Liens	0
Face amount of loans	3,958,016,000
Carrying amount of loans	$ 3,938,183,000
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	6,260,294,000
Carrying amount of loans	6,221,889,000
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	1,587,788,000
Carrying amount of loans	1,573,804,000
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	725,563,000
Carrying amount of loans	721,805,000
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	660,473,000
Carrying amount of loans	657,894,000
Various | Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,649,939,000
Face amount of loans	392,990,000
Carrying amount of loans	$ 388,947,000
Ireland | Mixed Use | 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	3.06%
Prior Liens	$ 0
Face amount of loans	1,033,286,000
Carrying amount of loans	$ 1,028,715,000
New York | Office | 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	4.49%
Prior Liens	$ 0
Face amount of loans	905,355,000
Carrying amount of loans	$ 898,541,000
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
Face amount of loans	901,360,000
Carrying amount of loans	$ 893,114,000
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	2.65%
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 Rates	2.00%
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	2.20%
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	1.60%
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	2.60%
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	2.25%
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 | Various | Subordinate Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.65%
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 | 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 Rates	5.00%
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	4.75%
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 | 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	3.18%
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	4.70%
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%