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	3 Months Ended	12 Months Ended
Mar. 31, 2023 USD ($) loan	Dec. 31, 2022 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	55	61
Total	$ 8,502,335	$ 8,708,214
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	100.00%	100.00%
Year 1	$ 172,260	$ 2,575,455
Year 2	2,606,091	2,462,499
Year 3	2,383,028	687,329
Year 4	676,366	1,637,050
Year 5	1,638,312	499,720
Prior	1,026,279	846,161
General CECL Allowance	(30,267)	(26,224)
Total carrying value, net	$ 8,472,068	$ 8,681,990
Weighted Average Risk Rating	3.0	3.0
Gross write-offs	$ 0	$ 7,000
Off-balance-sheet, credit loss, liability, amount excluded	$ 4,700	$ 4,300
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	3	2
Total	$ 195,584	$ 65,943
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	2.30%	0.80%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	129,712	0
Prior	$ 65,872	$ 65,943
3
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	47	54
Total	$ 8,081,606	$ 8,401,925
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	95.10%	96.50%
Year 1	$ 172,260	$ 2,575,455
Year 2	2,606,091	2,462,499
Year 3	2,383,028	687,329
Year 4	676,366	1,637,050
Year 5	1,508,600	479,769
Prior	$ 735,261	$ 559,823
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	3	2
Total	$ 110,762	$ 27,451
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.30%	0.30%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	19,951
Prior	$ 110,762	$ 7,500
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	2	3
Total	$ 114,383	$ 212,895
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.30%	2.40%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 114,383	$ 212,895

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