Segment reporting (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($) segment	Jun. 30, 2023 USD ($) segment	Jun. 30, 2024 USD ($) segment	Jun. 30, 2023 USD ($) segment
Segment reporting
Number of reportable segments | segment	2	2	2	2
Interest income	$ 234,119	$ 231,004	$ 466,473	$ 446,972
Interest expense	(183,167)	(170,221)	(366,972)	(329,089)
Net interest income before recovery of (provision for) loan losses	50,952	60,783	99,501	117,883
Recovery of (provision for) loan losses	18,871	(19,427)	45,415	(12,693)
Net interest income after recovery of (provision for) loan losses	69,823	41,356	144,916	105,190
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	7,250	23,878	26,118	35,453
Net unrealized gain (loss) on financial instruments	(1,357)	(1,411)	3,275	(7,046)
Valuation allowance, loans held for sale	(80,987)		(227,167)
Servicing income, net	3,271	5,039	7,029	9,681
Income (loss) from unconsolidated joint ventures	1,139	33	1,607	689
Other income	6,597	18,632	22,423	39,024
Gain (loss) on bargain purchase	(18,306)	229,894	(18,306)	229,894
Total non-interest income (expense)	(82,393)	276,065	(185,021)	307,695
Non-interest expense
Professional fees	(6,033)	(5,533)	(13,098)	(11,076)
Loan servicing expense	(11,012)	(10,894)	(23,806)	(19,049)
Transaction related expenses	(1,592)	(13,966)	(2,242)	(14,859)
Other operating expenses	(21,802)	(9,557)	(51,989)	(22,166)
Total non-interest expense	(67,436)	(70,695)	(145,694)	(126,749)
Income (loss) before provision for income taxes	(80,006)	246,726	(185,799)	286,136
Total assets	11,350,439	11,929,068	11,350,439	11,929,068
Nonrelated party
Non-interest expense
Employee compensation and benefits	(17,799)	(22,414)	(36,213)	(42,141)
Related Party
Non-interest expense
Employee compensation and benefits	(3,000)	(2,500)	(5,500)	(4,826)
Management fees - related party	(6,198)	(5,760)	(12,846)	(10,841)
Incentive fees - related party		(71)		(1,791)
Operating Segments | LMM Commercial Real Estate
Segment reporting
Interest income	202,047	212,233	402,810	410,272
Interest expense	(158,344)	(160,503)	(317,229)	(309,997)
Net interest income before recovery of (provision for) loan losses	43,703	51,730	85,581	100,275
Recovery of (provision for) loan losses	14,414	(17,415)	45,169	(9,286)
Net interest income after recovery of (provision for) loan losses	58,117	34,315	130,750	90,989
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	(10,089)	15,356	(4,334)	20,181
Net unrealized gain (loss) on financial instruments	(1,497)	(677)	1,489	(6,788)
Valuation allowance, loans held for sale	(80,987)		(227,167)
Servicing income, net	1,255	1,890	2,553	2,983
Income (loss) from unconsolidated joint ventures	1,139	33	1,607	689
Other income	4,796	8,167	17,523	17,260
Total non-interest income (expense)	(85,383)	24,769	(208,329)	34,325
Non-interest expense
Professional fees	(874)	(1,135)	(2,515)	(2,116)
Loan servicing expense	(10,896)	(10,746)	(23,443)	(18,804)
Other operating expenses	(12,054)	(3,598)	(33,588)	(10,331)
Total non-interest expense	(31,266)	(24,453)	(74,714)	(46,663)
Income (loss) before provision for income taxes	(58,532)	34,631	(152,293)	78,651
Total assets	9,527,088	10,969,193	9,527,088	10,969,193
Operating Segments | LMM Commercial Real Estate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(7,142)	(8,724)	(14,618)	(14,930)
Operating Segments | LMM Commercial Real Estate | Related Party
Non-interest expense
Employee compensation and benefits	(300)	(250)	(550)	(482)
Operating Segments | Small Business Lending
Segment reporting
Interest income	32,072	18,771	63,663	36,700
Interest expense	(24,823)	(9,718)	(49,743)	(19,092)
Net interest income before recovery of (provision for) loan losses	7,249	9,053	13,920	17,608
Recovery of (provision for) loan losses	4,457	(2,012)	246	(3,407)
Net interest income after recovery of (provision for) loan losses	11,706	7,041	14,166	14,201
Non-interest income
Net realized gain (loss) on financial instruments and real estate owned	17,339	8,522	30,452	15,272
Net unrealized gain (loss) on financial instruments	140	(734)	1,786	(258)
Servicing income, net	2,016	3,149	4,476	6,698
Other income	376	10,185	3,475	21,153
Total non-interest income (expense)	19,871	21,122	40,189	42,865
Non-interest expense
Professional fees	(2,930)	(2,782)	(6,145)	(4,407)
Loan servicing expense	(116)	(148)	(363)	(245)
Other operating expenses	(5,918)	(4,687)	(11,271)	(8,781)
Total non-interest expense	(17,292)	(19,231)	(35,399)	(36,322)
Income (loss) before provision for income taxes	14,285	8,932	18,956	20,744
Total assets	1,367,463	739,391	1,367,463	739,391
Operating Segments | Small Business Lending | Nonrelated party
Non-interest expense
Employee compensation and benefits	(8,328)	(11,614)	(17,620)	(22,889)
Corporate
Non-interest income
Other income	1,425	280	1,425	611
Gain (loss) on bargain purchase	(18,306)	229,894	(18,306)	229,894
Total non-interest income (expense)	(16,881)	230,174	(16,881)	230,505
Non-interest expense
Professional fees	(2,229)	(1,616)	(4,438)	(4,553)
Transaction related expenses	(1,592)	(13,966)	(2,242)	(14,859)
Other operating expenses	(3,830)	(1,272)	(7,130)	(3,054)
Total non-interest expense	(18,878)	(27,011)	(35,581)	(43,764)
Income (loss) before provision for income taxes	(35,759)	203,163	(52,462)	186,741
Total assets	455,888	220,484	455,888	220,484
Corporate | Nonrelated party
Non-interest expense
Employee compensation and benefits	(2,329)	(2,076)	(3,975)	(4,322)
Corporate | Related Party
Non-interest expense
Employee compensation and benefits	(2,700)	(2,250)	(4,950)	(4,344)
Management fees - related party	$ (6,198)	(5,760)	$ (12,846)	(10,841)
Incentive fees - related party		$ (71)		$ (1,791)