Interest income and interest expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest income
Total loans	$ 59,379	$ 54,237	$ 125,816	$ 100,439
Total loans, held for sale, at fair value	2,378	1,282	4,014	2,351
Mortgage backed securities, at fair value	1,454	1,515	2,932	2,997
Total interest income	63,211	57,034	132,762	105,787
Interest expense
Secured borrowings	(13,539)	(11,540)	(26,297)	(21,449)
Securitized debt obligations of consolidated VIEs	(17,317)	(17,038)	(36,846)	(33,539)
Guaranteed loan financing	(4,153)	(518)	(10,396)	(3,228)
Senior secured note	(3,469)	(3,481)	(6,941)	(6,965)
Convertible note	(2,188)	(2,188)	(4,376)	(4,376)
Corporate debt	(2,742)	(988)	(5,482)	(1,972)
Total interest expense	(43,408)	(35,753)	(90,338)	(71,529)
Net interest income before provision for loan losses	19,803	21,281	42,424	34,258
Acquired SBA 7(a) loans
Interest income
Total loans	3,949	4,288	10,151	11,469
Acquired loans
Interest income
Total loans	13,924	17,789	29,335	28,042
Total loans, held for sale, at fair value	58	37	126	73
Originated Transitional loans
Interest income
Total loans	22,368	17,056	44,587	31,241
Originated SBC loans, at fair value
Interest income
Total loans	515	354	832	721
Originated SBC loans
Interest income
Total loans	13,930	11,898	29,928	24,180
Originated SBA 7(a) loans
Interest income
Total loans	4,665	2,836	10,934	4,764
Originated Residential Agency loans
Interest income
Total loans	28	16	49	22
Total loans, held for sale, at fair value	1,901	1,047	3,198	1,823
Originated Freddie Mac loans
Interest income
Total loans, held for sale, at fair value	$ 419	$ 198	$ 690	$ 455