LOANS HELD-FOR-INVESTMENT - Allowance for Financing Receivable (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended	12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value			$ 4,264,465				$ 4,264,465
Provision for (reversal of) credit losses							246,533
Charge-offs of CECL	$ (2,860)	$ (480)	(1,649)				(4,989)
Ending Balance, Net Book Value	3,468,361						3,468,361	$ 4,264,465
Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	420,761	208,871	143,158	$ 72,315	$ 46,130	$ 44,677	143,158	44,677
Provision for (reversal of) credit losses	(22,614)	212,370	67,362	47,923	26,185	1,453
Ending Balance, Net Book Value	395,287	420,761	208,871	120,238	72,315	46,130	395,287	143,158
First Mortgage Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs of CECL	0	0	0
First Mortgage Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	398,289	186,804	109,240	44,769	22,301	20,352	109,240	20,352
Provision for (reversal of) credit losses	(24,304)	211,485	77,564	45,651	22,468	1,949
Ending Balance, Net Book Value	373,985	398,289	186,804	90,420	44,769	22,301	373,985	109,240
Unfunded First Mortgage Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs of CECL	0	0	0
Unfunded First Mortgage Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	10,606	3,409	10,062	4,168	2,028	1,890	10,062	1,890
Provision for (reversal of) credit losses	5,029	7,197	(6,653)	5,030	2,140	138
Ending Balance, Net Book Value	15,635	10,606	3,409	9,198	4,168	2,028	15,635	10,062
Liquid Corporate Senior Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value			518,252				518,252
Provision for (reversal of) credit losses							(18,721)
Charge-offs of CECL	(2,860)	(480)	(1,649)				(4,989)
Ending Balance, Net Book Value	51,083						51,083	518,252
Liquid Corporate Senior Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	7,927	14,370	19,738	20,832	20,281	21,195	19,738	21,195
Provision for (reversal of) credit losses	(4,050)	(5,963)	(3,719)	(2,841)	551	(914)
Ending Balance, Net Book Value	1,017	7,927	14,370	17,991	20,832	20,281	1,017	19,738
Unfunded or Unsettled Liquid Senior Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs of CECL	0	0	0
Unfunded or Unsettled Liquid Senior Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	1	2	3	259	256	377	3	377
Provision for (reversal of) credit losses	(1)	(1)	(1)	(259)	3	(121)
Ending Balance, Net Book Value	0	1	2	0	259	256	0	3
Corporate Senior Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value			207,102				207,102
Provision for (reversal of) credit losses							509
Charge-offs of CECL	0	0	0				0
Ending Balance, Net Book Value	229,788						229,788	207,102
Corporate Senior Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	3,534	3,869	3,620	1,961	1,197	797	3,620	797
Provision for (reversal of) credit losses	595	(335)	249	338	764	400
Ending Balance, Net Book Value	4,129	3,534	3,869	2,299	1,961	1,197	4,129	3,620
Unfunded Corporate Senior Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Charge-offs of CECL	0	0	0
Unfunded Corporate Senior Loans | Gross Credit Losses
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance, Net Book Value	404	417	495	326	67	66	495	66
Provision for (reversal of) credit losses	117	(13)	(78)	4	259	1
Ending Balance, Net Book Value	$ 521	$ 404	$ 417	$ 330	$ 326	$ 67	$ 521	$ 495