Segment Reporting (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment reporting
Number of reportable segments | segment	2
Interest income	$ 945,814	$ 663,217	$ 395,196
Interest expense	(716,468)	(392,360)	(204,368)
Net interest income before provision for loan losses	229,346	270,857	190,828
Provision for loan losses	(7,230)	(34,442)	(8,049)
Net interest income after provision for loan losses	222,116	236,415	182,779
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	65,008	53,764	68,881
Net unrealized gain (loss) on financial instruments	9,718	21,890	22,457
Servicing income, net	21,161	11,428	17,623
Income on purchased future receivables, net	2,387	5,490	10,257
Income (loss) from unconsolidated joint ventures	(905)	11,661	6,916
Other income (loss)	103,127	50,718	6,856
Gain on bargain purchase	207,972
Total non-interest income	408,468	154,951	132,990
Non-interest expense
Professional fees	(34,738)	(17,302)	(13,388)
Loan servicing expense	(40,811)	(30,814)	(20,566)
Transaction related expenses	(17,764)	(13,633)	(14,282)
Other operating expenses	(59,591)	(47,653)	(49,903)
Total non-interest expense	(272,165)	(216,340)	(183,609)
Income (loss) before provision for income taxes	358,419	175,026	132,160
Total assets	11,986,621	11,181,786	9,015,285
Nonrelated party
Non-interest expense
Employee compensation and benefits	(81,530)	(74,989)	(57,092)
Related Party
Non-interest expense
Employee compensation and benefits	(10,837)	(9,549)	(12,031)
Management fees - related party	(25,103)	(19,295)	(10,928)
Incentive fees - related party	(1,791)	(3,105)	(5,419)
Operating Segments | LMM Commercial Real Estate
Segment reporting
Interest income	847,253	565,128	278,455
Interest expense	(650,624)	(364,343)	(164,797)
Net interest income before provision for loan losses	196,629	200,785	113,658
Provision for loan losses	(1,413)	(31,471)	(7,387)
Net interest income after provision for loan losses	195,216	169,314	106,271
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	34,072	21,813	24,813
Net unrealized gain (loss) on financial instruments	8,427	23,321	19,458
Servicing income, net	5,819	4,623	3,113
Income (loss) from unconsolidated joint ventures	(905)	11,661	6,916
Other income (loss)	38,552	29,506	13,002
Total non-interest income	85,965	90,924	67,302
Non-interest expense
Professional fees	(5,369)	(7,030)	(4,064)
Loan servicing expense	(40,070)	(30,107)	(19,680)
Other operating expenses	(24,443)	(23,761)	(21,997)
Total non-interest expense	(103,776)	(91,270)	(63,526)
Income (loss) before provision for income taxes	177,405	168,968	110,047
Total assets	10,282,531	10,197,876	7,106,206
Operating Segments | LMM Commercial Real Estate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(33,012)	(29,417)	(16,582)
Operating Segments | LMM Commercial Real Estate | Related Party
Non-interest expense
Employee compensation and benefits	(882)	(955)	(1,203)
Operating Segments | Small Business Lending
Segment reporting
Interest income	98,561	98,089	116,741
Interest expense	(65,844)	(27,382)	(36,872)
Net interest income before provision for loan losses	32,717	70,707	79,869
Provision for loan losses	(5,817)	(2,971)	(662)
Net interest income after provision for loan losses	26,900	67,736	79,207
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	30,936	31,951	44,068
Net unrealized gain (loss) on financial instruments	1,291	(1,431)	2,999
Servicing income, net	15,342	6,805	14,510
Income on purchased future receivables, net	2,387	5,490	10,257
Other income (loss)	62,112	20,382	(6,231)
Total non-interest income	112,068	63,197	65,603
Non-interest expense
Professional fees	(19,535)	(5,361)	(3,034)
Loan servicing expense	(741)	(707)	(886)
Other operating expenses	(27,763)	(17,776)	(23,377)
Total non-interest expense	(88,328)	(64,390)	(64,054)
Income (loss) before provision for income taxes	50,640	66,543	80,756
Total assets	1,395,687	835,836	1,558,641
Operating Segments | Small Business Lending | Nonrelated party
Non-interest expense
Employee compensation and benefits	(40,289)	(40,546)	(36,757)
Corporate
Segment reporting
Interest expense		(635)	(2,699)
Net interest income before provision for loan losses		(635)	(2,699)
Net interest income after provision for loan losses		(635)	(2,699)
Non-interest income
Other income (loss)	2,463	830	85
Gain on bargain purchase	207,972
Total non-interest income	210,435	830	85
Non-interest expense
Professional fees	(9,834)	(4,911)	(6,290)
Transaction related expenses	(17,764)	(13,633)	(14,282)
Other operating expenses	(7,385)	(6,116)	(4,529)
Total non-interest expense	(80,061)	(60,680)	(56,029)
Income (loss) before provision for income taxes	130,374	(60,485)	(58,643)
Total assets	308,403	148,074	350,438
Corporate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(8,229)	(5,026)	(3,753)
Corporate | Related Party
Non-interest expense
Employee compensation and benefits	(9,955)	(8,594)	(10,828)
Management fees - related party	(25,103)	(19,295)	(10,928)
Incentive fees - related party	$ (1,791)	$ (3,105)	$ (5,419)