Schedule IV - Mortgage Loans on Real Estate - Product Type (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	5,560
UPB	$ 7,644,183
UPB of loans subject to DQ principal or interest	202,598
General allowance for loan losses	(28,113)	$ (29,539)
Total Loans	$ 7,550,229	$ 4,363,719	$ 4,246,694	$ 2,529,624
Acquired loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1,871
Carrying Value	$ 1,193,641
UPB	1,201,816
UPB of loans subject to DQ principal or interest	$ 48,854
Acquired loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1,412
Carrying Value	$ 286,054
UPB	289,410
UPB of loans subject to DQ principal or interest	$ 17,282
Acquired loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	1.00%
Acquired loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	11.50%
Acquired loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	265
Carrying Value	$ 181,979
UPB	181,598
UPB of loans subject to DQ principal or interest	$ 9,208
Acquired loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.88%
Acquired loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	8.00%
Acquired loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	88
Carrying Value	$ 105,812
UPB	106,449
UPB of loans subject to DQ principal or interest	$ 7,054
Acquired loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	1.00%
Acquired loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	8.50%
Acquired loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	28
Carrying Value	$ 48,357
UPB	48,570
UPB of loans subject to DQ principal or interest	$ 3,104
Acquired loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	2.20%
Acquired loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	10.25%
Acquired loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	15
Carrying Value	$ 33,711
UPB	33,630
UPB of loans subject to DQ principal or interest	$ 2,206
Acquired loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	2.49%
Acquired loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.75%
Acquired loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	63
Carrying Value	$ 537,728
UPB	542,159
UPB of loans subject to DQ principal or interest	$ 10,000
Acquired loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.13%
Acquired loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	11.00%
Acquired SBA 7(a) loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	824
Carrying Value	$ 182,554
UPB	197,828
UPB of loans subject to DQ principal or interest	$ 7,248
Acquired SBA 7(a) loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	720
Carrying Value	$ 83,596
UPB	94,536
UPB of loans subject to DQ principal or interest	$ 5,467
Acquired SBA 7(a) loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	0.00%
Acquired SBA 7(a) loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	8.75%
Acquired SBA 7(a) loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	80
Carrying Value	$ 54,288
UPB	57,425
UPB of loans subject to DQ principal or interest	$ 1,781
Acquired SBA 7(a) loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.75%
Acquired SBA 7(a) loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.50%
Acquired SBA 7(a) loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	13
Carrying Value	$ 14,638
UPB	$ 15,341
Acquired SBA 7(a) loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.00%
Acquired SBA 7(a) loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Acquired SBA 7(a) loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	3
Carrying Value	$ 5,325
UPB	$ 5,402
Acquired SBA 7(a) loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Acquired SBA 7(a) loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Acquired SBA 7(a) loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	2
Carrying Value	$ 4,541
UPB	$ 4,599
Acquired SBA 7(a) loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.00%
Acquired SBA 7(a) loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.75%
Acquired SBA 7(a) loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	6
Carrying Value	$ 20,166
UPB	$ 20,525
Acquired SBA 7(a) loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.75%
Acquired SBA 7(a) loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.25%
Originated Transitional loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	436
Carrying Value	$ 4,382,282
UPB	4,422,524
UPB of loans subject to DQ principal or interest	$ 97,476
Originated Transitional loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	62
Carrying Value	$ 11,077
UPB	$ 11,089
Originated Transitional loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.15%
Originated Transitional loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.00%
Originated Transitional loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	22
Carrying Value	$ 15,325
UPB	15,412
UPB of loans subject to DQ principal or interest	$ 1,227
Originated Transitional loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.30%
Originated Transitional loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	105.10%
Originated Transitional loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	11
Carrying Value	$ 13,536
UPB	$ 13,629
Originated Transitional loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.85%
Originated Transitional loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.90%
Originated Transitional loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	17
Carrying Value	$ 30,241
UPB	30,519
UPB of loans subject to DQ principal or interest	$ 1,995
Originated Transitional loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.10%
Originated Transitional loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	8.10%
Originated Transitional loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	15
Carrying Value	$ 33,052
UPB	33,371
UPB of loans subject to DQ principal or interest	$ 2,364
Originated Transitional loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.00%
Originated Transitional loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	12.00%
Originated Transitional loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	309
Carrying Value	$ 4,279,051
UPB	4,318,504
UPB of loans subject to DQ principal or interest	$ 91,890
Originated Transitional loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.00%
Originated Transitional loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	9.25%
Originated Freddie Mac loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	14
Carrying Value	$ 42,384
UPB	$ 41,864
Originated Freddie Mac loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	4
Carrying Value	$ 5,012
UPB	$ 4,949
Originated Freddie Mac loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.18%
Originated Freddie Mac loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.47%
Originated Freddie Mac loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1
Carrying Value	$ 1,605
UPB	$ 1,589
Originated Freddie Mac loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.23%
Originated Freddie Mac loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.23%
Originated Freddie Mac loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	2
Carrying Value	$ 4,213
UPB	$ 4,171
Originated Freddie Mac loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.17%
Originated Freddie Mac loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.21%
Originated Freddie Mac loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	7
Carrying Value	$ 31,554
UPB	$ 31,155
Originated Freddie Mac loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.35%
Originated Freddie Mac loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.63%
Originated Residential Agency loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1,057
Carrying Value	$ 238,491
UPB	233,762
UPB of loans subject to DQ principal or interest	$ 1,663
Originated Residential Agency loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1,019
Carrying Value	$ 214,463
UPB	210,194
UPB of loans subject to DQ principal or interest	$ 1,663
Originated Residential Agency loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	2.13%
Originated Residential Agency loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.50%
Originated Residential Agency loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	38
Carrying Value	$ 24,028
UPB	$ 23,568
Originated Residential Agency loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	2.13%
Originated Residential Agency loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.99%
Originated SBA 7(a) loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1,062
Carrying Value	$ 447,019
UPB	459,150
UPB of loans subject to DQ principal or interest	$ 8,399
Originated SBA 7(a) loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	805
Carrying Value	$ 139,128
UPB	147,119
UPB of loans subject to DQ principal or interest	$ 3,859
Originated SBA 7(a) loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	0.00%
Originated SBA 7(a) loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.50%
Originated SBA 7(a) loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	138
Carrying Value	$ 97,311
UPB	99,969
UPB of loans subject to DQ principal or interest	$ 1,998
Originated SBA 7(a) loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.25%
Originated SBA 7(a) loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Originated SBA 7(a) loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	63
Carrying Value	$ 74,344
UPB	$ 75,909
Originated SBA 7(a) loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.00%
Originated SBA 7(a) loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Originated SBA 7(a) loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	19
Carrying Value	$ 32,678
UPB	$ 32,675
Originated SBA 7(a) loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.25%
Originated SBA 7(a) loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Originated SBA 7(a) loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	17
Carrying Value	$ 39,196
UPB	$ 39,026
Originated SBA 7(a) loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.50%
Originated SBA 7(a) loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Originated SBA 7(a) loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	20
Carrying Value	$ 64,362
UPB	64,452
UPB of loans subject to DQ principal or interest	$ 2,542
Originated SBA 7(a) loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.50%
Originated SBA 7(a) loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.00%
Originated SBC loans
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	280
Carrying Value	$ 980,033
UPB	975,628
UPB of loans subject to DQ principal or interest	$ 38,958
Originated SBC loans | 0 - 500k
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	18
Carrying Value	$ 4,899
UPB	$ 4,837
Originated SBC loans | 0 - 500k | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.25%
Originated SBC loans | 0 - 500k | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	8.10%
Originated SBC loans | 500k - 1mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	32
Carrying Value	$ 26,034
UPB	25,679
UPB of loans subject to DQ principal or interest	$ 709
Originated SBC loans | 500k - 1mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.50%
Originated SBC loans | 500k - 1mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	9.22%
Originated SBC loans | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	43
Carrying Value	$ 52,724
UPB	52,309
UPB of loans subject to DQ principal or interest	$ 4,316
Originated SBC loans | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.68%
Originated SBC loans | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	10.00%
Originated SBC loans | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	36
Carrying Value	$ 62,180
UPB	62,353
UPB of loans subject to DQ principal or interest	$ 1,560
Originated SBC loans | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.25%
Originated SBC loans | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.43%
Originated SBC loans | 2mm - 2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	27
Carrying Value	$ 61,377
UPB	60,837
UPB of loans subject to DQ principal or interest	$ 2,224
Originated SBC loans | 2mm - 2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.60%
Originated SBC loans | 2mm - 2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	6.06%
Originated SBC loans | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	124
Carrying Value	$ 772,819
UPB	769,613
UPB of loans subject to DQ principal or interest	$ 30,149
Originated SBC loans | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.73%
Originated SBC loans | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.50%
Originated SBC loans, at fair value
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	16
Carrying Value	$ 111,938
UPB	$ 111,611
Originated SBC loans, at fair value | 1mm - 1.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	1
Carrying Value	$ 1,337
UPB	$ 1,337
Originated SBC loans, at fair value | 1mm - 1.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.25%
Originated SBC loans, at fair value | 1mm - 1.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.25%
Originated SBC loans, at fair value | 1.5mm - 2mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	2
Carrying Value	$ 4,023
UPB	$ 4,023
Originated SBC loans, at fair value | 1.5mm - 2mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	4.59%
Originated SBC loans, at fair value | 1.5mm - 2mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	5.27%
Originated SBC loans, at fair value | >2.5mm
Schedule IV - Mortgage Loans on Real Estate
Loan Count | loan	13
Carrying Value	$ 106,578
UPB	$ 106,251
Originated SBC loans, at fair value | >2.5mm | Minimum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	3.51%
Originated SBC loans, at fair value | >2.5mm | Maximum
Schedule IV - Mortgage Loans on Real Estate
Interest Rate	7.75%