FAIR VALUE OF FINANCIAL INSTRUMENTS - Summary of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets:
Fair value of assets	$ 3,922,131	$ 3,516,524
Liabilities:
Fair value of liabilities	3,994,458	4,282,888
Repurchase agreements - short-term
Liabilities:
Principal Amount	481,465	418,394
Fair value of liabilities	481,465	418,394
Mortgage loan financing
Liabilities:
Principal Amount	497,454	690,927
Fair value of liabilities	477,101	709,695
CLO debt
Liabilities:
Principal Amount	1,064,365	1,064,365
Fair value of liabilities	1,058,462	1,054,774
Borrowings from the FHLB
Liabilities:
Principal Amount	213,000	263,000
Fair value of liabilities	213,055	263,414
Senior unsecured notes
Liabilities:
Principal Amount	1,643,794	1,649,794
Fair value of liabilities	1,397,977	1,677,039
Repurchase agreements - long-term
Liabilities:
Principal Amount	366,398	26,183
Fair value of liabilities	366,398	26,183
Secured financing facility
Liabilities:
Principal Amount		136,444
Fair value of liabilities		133,389
CMBS
Assets:
Principal Amount	9,415	10,326
Fair value of assets	9,030	9,894
CMBS interest-only
Assets:
Principal Amount	8,460	9,370
Fair value of assets	417	541
Total mortgage loan receivables held for investment, net, at amortized cost
Assets:
Principal Amount	3,907,295	3,581,920
Fair value of assets	3,875,708	3,494,254
FHLB stock
Assets:
Principal Amount	9,585	11,835
Fair value of assets	9,585	11,835
Mortgage loan  receivables held for sale
Assets:
Principal Amount	31,350
Fair value of assets	27,391
Level 1
Assets:
Fair value of assets	0	0
Liabilities:
Fair value of liabilities	0	0
Level 1 | Repurchase agreements - short-term
Liabilities:
Fair value of liabilities	0	0
Level 1 | Mortgage loan financing
Liabilities:
Fair value of liabilities	0	0
Level 1 | CLO debt
Liabilities:
Fair value of liabilities	0	0
Level 1 | Borrowings from the FHLB
Liabilities:
Fair value of liabilities	0	0
Level 1 | Senior unsecured notes
Liabilities:
Fair value of liabilities	0	0
Level 1 | Repurchase agreements - long-term
Liabilities:
Fair value of liabilities	0	0
Level 1 | Secured financing facility
Liabilities:
Fair value of liabilities		0
Level 1 | CMBS
Assets:
Fair value of assets	0	0
Level 1 | CMBS interest-only
Assets:
Fair value of assets	0	0
Level 1 | Total mortgage loan receivables held for investment, net, at amortized cost
Assets:
Fair value of assets	0	0
Level 1 | FHLB stock
Assets:
Fair value of assets	0	0
Level 1 | Mortgage loan  receivables held for sale
Assets:
Fair value of assets	0
Level 2
Assets:
Fair value of assets	0	0
Liabilities:
Fair value of liabilities	0	0
Level 2 | Repurchase agreements - short-term
Liabilities:
Fair value of liabilities	0	0
Level 2 | Mortgage loan financing
Liabilities:
Fair value of liabilities	0	0
Level 2 | CLO debt
Liabilities:
Fair value of liabilities	0	0
Level 2 | Borrowings from the FHLB
Liabilities:
Fair value of liabilities	0	0
Level 2 | Senior unsecured notes
Liabilities:
Fair value of liabilities	0	0
Level 2 | Repurchase agreements - long-term
Liabilities:
Fair value of liabilities	0	0
Level 2 | Secured financing facility
Liabilities:
Fair value of liabilities		0
Level 2 | CMBS
Assets:
Fair value of assets	0	0
Level 2 | CMBS interest-only
Assets:
Fair value of assets	0	0
Level 2 | Total mortgage loan receivables held for investment, net, at amortized cost
Assets:
Fair value of assets	0	0
Level 2 | FHLB stock
Assets:
Fair value of assets	0	0
Level 2 | Mortgage loan  receivables held for sale
Assets:
Fair value of assets	0
Level 3
Assets:
Fair value of assets	3,922,131	3,516,524
Liabilities:
Fair value of liabilities	3,994,458	4,282,888
Level 3 | Repurchase agreements - short-term
Liabilities:
Fair value of liabilities	481,465	418,394
Level 3 | Mortgage loan financing
Liabilities:
Fair value of liabilities	477,101	709,695
Level 3 | CLO debt
Liabilities:
Fair value of liabilities	1,058,462	1,054,774
Level 3 | Borrowings from the FHLB
Liabilities:
Fair value of liabilities	213,055	263,414
Level 3 | Senior unsecured notes
Liabilities:
Fair value of liabilities	1,397,977	1,677,039
Level 3 | Repurchase agreements - long-term
Liabilities:
Fair value of liabilities	366,398	26,183
Level 3 | Secured financing facility
Liabilities:
Fair value of liabilities		133,389
Level 3 | CMBS
Assets:
Fair value of assets	9,030	9,894
Level 3 | CMBS interest-only
Assets:
Fair value of assets	417	541
Level 3 | Total mortgage loan receivables held for investment, net, at amortized cost
Assets:
Fair value of assets	3,875,708	3,494,254
Level 3 | FHLB stock
Assets:
Fair value of assets	9,585	11,835
Level 3 | Mortgage loan  receivables held for sale
Assets:
Fair value of assets	27,391
Recurring
Assets:
Fair value of assets	580,130	693,266
Recurring | CMBS
Assets:
Principal Amount	553,424	681,076
Fair value of assets	532,304	676,398
Recurring | CMBS interest-only
Assets:
Principal Amount	1,017,735	1,293,181
Fair value of assets	10,026	15,344
Recurring | GNMA interest-only
Assets:
Principal Amount	45,369	59,075
Fair value of assets	281	559
Recurring | Agency securities
Assets:
Principal Amount	36	557
Fair value of assets	35	563
Recurring | U.S. Treasury securities
Assets:
Principal Amount	36,000
Fair value of assets	35,328
Recurring | Equity Securities
Assets:
Fair value of assets	118
Recurring | Nonhedge derivatives
Assets:
Principal Amount	204,700
Fair value of assets	2,038	402
Nonhedge derivative assets		114,121
Recurring | Level 1
Assets:
Fair value of assets	35,446	0
Recurring | Level 1 | CMBS
Assets:
Fair value of assets	0	0
Recurring | Level 1 | CMBS interest-only
Assets:
Fair value of assets	0	0
Recurring | Level 1 | GNMA interest-only
Assets:
Fair value of assets	0	0
Recurring | Level 1 | Agency securities
Assets:
Fair value of assets	0	0
Recurring | Level 1 | U.S. Treasury securities
Assets:
Fair value of assets	35,328
Recurring | Level 1 | Equity Securities
Assets:
Fair value of assets	118
Recurring | Level 1 | Nonhedge derivatives
Assets:
Fair value of assets	0	0
Recurring | Level 2
Assets:
Fair value of assets	2,038	402
Recurring | Level 2 | CMBS
Assets:
Fair value of assets	0	0
Recurring | Level 2 | CMBS interest-only
Assets:
Fair value of assets	0	0
Recurring | Level 2 | GNMA interest-only
Assets:
Fair value of assets	0	0
Recurring | Level 2 | Agency securities
Assets:
Fair value of assets	0	0
Recurring | Level 2 | U.S. Treasury securities
Assets:
Fair value of assets	0
Recurring | Level 2 | Equity Securities
Assets:
Fair value of assets	0
Recurring | Level 2 | Nonhedge derivatives
Assets:
Fair value of assets	2,038	402
Recurring | Level 3
Assets:
Fair value of assets	542,646	692,864
Recurring | Level 3 | CMBS
Assets:
Fair value of assets	532,304	676,398
Recurring | Level 3 | CMBS interest-only
Assets:
Fair value of assets	10,026	15,344
Recurring | Level 3 | GNMA interest-only
Assets:
Fair value of assets	281	559
Recurring | Level 3 | Agency securities
Assets:
Fair value of assets	35	563
Recurring | Level 3 | U.S. Treasury securities
Assets:
Fair value of assets	0
Recurring | Level 3 | Equity Securities
Assets:
Fair value of assets	0
Recurring | Level 3 | Nonhedge derivatives
Assets:
Fair value of assets	$ 0	$ 0