Segment reporting (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) segment	Mar. 31, 2023 USD ($) segment
Segment reporting
Number of reportable segments | segment	2	2
Interest income	$ 232,354	$ 215,968
Interest expense	(183,805)	(158,868)
Net interest income before recovery of loan losses	48,549	57,100
Recovery of (provision for) loan losses	26,544	6,734
Net interest income after recovery of loan losses	75,093	63,834
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	18,868	11,575
Net unrealized gain (loss) on financial instruments	4,632	(5,635)
Valuation allowance, loans held for sale	(146,180)
Servicing income, net	3,758	4,642
Income on purchased future receivables, net	446	540
Income (loss) from unconsolidated joint ventures	468	656
Other income	15,380	19,852
Total non-interest income	(102,628)	31,630
Non-interest expense
Professional fees	(7,065)	(5,543)
Loan servicing expense	(12,794)	(8,155)
Transaction related expenses	(650)	(893)
Other operating expenses	(30,187)	(12,609)
Total non-interest expense	(78,258)	(56,054)
Income (loss) before provision for income taxes	(105,793)	39,410
Total assets	11,604,231	11,080,783
Nonrelated party
Non-interest expense
Employee compensation and benefits	(18,414)	(19,727)
Related Party
Non-interest expense
Employee compensation and benefits	(2,500)	(2,326)
Management fees - related party	(6,648)	(5,081)
Incentive fees - related party		(1,720)
Operating Segments | LMM Commercial Real Estate
Segment reporting
Interest income	200,763	198,039
Interest expense	(158,885)	(149,494)
Net interest income before recovery of loan losses	41,878	48,545
Recovery of (provision for) loan losses	30,755	8,129
Net interest income after recovery of loan losses	72,633	56,674
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	5,755	4,825
Net unrealized gain (loss) on financial instruments	2,986	(6,111)
Valuation allowance, loans held for sale	(146,180)
Servicing income, net	1,298	1,093
Income (loss) from unconsolidated joint ventures	468	656
Other income	12,727	9,093
Total non-interest income	(122,946)	9,556
Non-interest expense
Professional fees	(1,641)	(981)
Loan servicing expense	(12,547)	(8,058)
Other operating expenses	(21,534)	(6,733)
Total non-interest expense	(43,448)	(22,210)
Income (loss) before provision for income taxes	(93,761)	44,020
Total assets	9,905,732	10,184,788
Operating Segments | LMM Commercial Real Estate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(7,476)	(6,206)
Operating Segments | LMM Commercial Real Estate | Related Party
Non-interest expense
Employee compensation and benefits	(250)	(232)
Operating Segments | Small Business Lending
Segment reporting
Interest income	31,591	17,929
Interest expense	(24,920)	(9,374)
Net interest income before recovery of loan losses	6,671	8,555
Recovery of (provision for) loan losses	(4,211)	(1,395)
Net interest income after recovery of loan losses	2,460	7,160
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	13,113	6,750
Net unrealized gain (loss) on financial instruments	1,646	476
Servicing income, net	2,460	3,549
Income on purchased future receivables, net	446	540
Other income	2,653	10,428
Total non-interest income	20,318	21,743
Non-interest expense
Professional fees	(3,215)	(1,625)
Loan servicing expense	(247)	(97)
Other operating expenses	(5,353)	(4,094)
Total non-interest expense	(18,107)	(17,091)
Income (loss) before provision for income taxes	4,671	11,812
Total assets	1,357,398	791,394
Operating Segments | Small Business Lending | Nonrelated party
Non-interest expense
Employee compensation and benefits	(9,292)	(11,275)
Corporate
Non-interest income
Other income		331
Total non-interest income		331
Non-interest expense
Professional fees	(2,209)	(2,937)
Transaction related expenses	(650)	(893)
Other operating expenses	(3,300)	(1,782)
Total non-interest expense	(16,703)	(16,753)
Income (loss) before provision for income taxes	(16,703)	(16,422)
Total assets	341,101	104,601
Corporate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(1,646)	(2,246)
Corporate | Related Party
Non-interest expense
Employee compensation and benefits	(2,250)	(2,094)
Management fees - related party	$ (6,648)	(5,081)
Incentive fees - related party		$ (1,720)