Commercial Mortgage Loans, Subordinate Loans and Other Lending Assets, Net - Allocation of Carrying Value of Loan Portfolio Based on Internal Risk Ratings (Details) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2024 USD ($) Loan	Dec. 31, 2023 USD ($) Loan
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	45	50
Total	$ 7,864,803	$ 8,384,575
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	100.00%	100.00%
Year 1	$ 974,717	$ 440,720
Year 2	660,811	2,707,083
Year 3	2,255,390	2,285,902
Year 4	1,860,024	557,204
Year 5	434,790	1,597,927
Prior	1,679,071	795,739
General CECL Allowance	(34,192)	(26,482)
Carrying value, net	$ 7,830,611	$ 8,358,093
Weighted-Average Risk Rating	3	3
Gross write-offs	$ 0	$ 81,890
1
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	0	0
Total	$ 0	$ 0
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	0.00%	0.00%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 0	$ 0
2
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	2	4
Total	$ 474,460	$ 478,440
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	6.00%	5.70%
Year 1	$ 0	$ 0
Year 2	0	280,572
Year 3	459,782	0
Year 4	14,678	0
Year 5	0	132,309
Prior	$ 0	$ 65,560
3
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	38	42
Total	$ 6,966,537	$ 7,548,252
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	88.60%	90.00%
Year 1	$ 974,717	$ 440,720
Year 2	660,811	2,426,511
Year 3	1,795,608	2,285,902
Year 4	1,845,346	387,323
Year 5	406,909	1,465,618
Prior	$ 1,283,146	$ 542,177
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	2	2
Total	$ 297,806	$ 88,112
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	3.80%	1.10%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 297,806	$ 88,112
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| Loan	3	2
Total	$ 126,000	$ 269,771
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.60%	3.20%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	169,881
Year 5	27,881	0
Prior	$ 98,119	$ 99,890

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