MORTGAGE LOAN RECEIVABLES - Individually Impaired Loans (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2023 USD ($) property	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2023 property
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	$ 3,155,089	$ 3,885,746
Subtotal loans, Year One		14,461	1,145,229
Subtotal loans, Year Two		919,738	2,102,307
Subtotal loans, Year Three		1,784,006	56,150
Subtotal loans, Year Four		0	332,046
Subtotal loans, Year 5 and Earlier		436,884	224,002
Subtotal mortgage loans receivable		3,155,089	3,859,734
Individually impaired loans, Year One		0	0
Individually impaired loans, Year Two		0	0
Individually impaired loans, Year Three		0	0
Individually impaired loans, Year Four		0	0
Individually impaired loans, Year Five and Earlier		0	26,012
Individually impaired loans		0	26,012
Total loans, Year One		14,461	1,145,229
Total loans, Year Two		919,738	2,102,307
Total loans, Year Three		1,784,006	56,150
Total loans, Year Four		0	332,046
Total loans, Year Five and Earlier		436,884	250,014
Write-off		2,700	14,395	$ 0
Accrued interest receivable		$ 22,400	23,200
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Accrued interest receivable
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		$ 14,461	702,125
Year Two		547,532	722,862
Year Three		612,489	0
Year Four		0	0
Year Five and Earlier		0	0
Total loans		1,174,482	1,424,987
Office
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	78,754
Year Two		79,148	676,431
Year Three		614,743	29,650
Year Four		0	58,684
Year Five and Earlier		211,674	136,512
Total loans		905,565	980,031
Mixed Use
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	201,777
Year Two		193,470	351,291
Year Three		321,514	26,500
Year Four		0	120,300
Year Five and Earlier		41,403	0
Total loans		556,387	699,868
Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	37,616
Year Two		22,636	96,486
Year Three		34,746	0
Year Four		0	115,545
Year Five and Earlier		119,344	0
Total loans		176,726	249,647
Manufactured Housing
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	32,515
Year Two		32,655	82,618
Year Three		82,895	0
Year Four		0	2,921
Year Five and Earlier		0	0
Total loans		115,550	118,054
Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	60,089
Year Two		12,934	107,305
Year Three		87,052	0
Year Four		0	12,953
Year Five and Earlier		9,083	9,126
Total loans		109,069	189,473
Hospitality
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	0
Year Two		0	45,416
Year Three		18,589	0
Year Four		0	13,843
Year Five and Earlier		55,380	78,364
Total loans		73,969	137,623
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Year One		0	32,353
Year Two		31,363	19,898
Year Three		11,978	0
Year Four		0	7,800
Year Five and Earlier		0	0
Total loans		43,341	$ 60,051
New York, NY
Financing Receivable, Credit Quality Indicator [Line Items]
Write-off		$ 2,700
Number of real estate properties | property		1
New York, NY | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Number of real estate properties | property					4

[1] Includes amounts relating to consolidated variable interest entities. Refer to Note 2 and Note 9.