Servicing rights - Assumptions (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
SBA servicing rights
Adverse changes to key assumptions on the carrying amount of the servicing rights
Prepayment rate (10% adverse change)	$ (690)	$ (543)
Prepayment rate (20% adverse change)	(1,355)	(1,069)
Default rate (10% adverse change)	(184)	(165)
Default rate (20% adverse change)	(366)	(328)
Discount rate (10% adverse change)	(1,514)	(1,530)
Discount rate (20% adverse change)	(2,905)	(2,922)
Cost of servicing (10% adverse change)	(2,260)	(2,047)
Cost of servicing (20% adverse change)	(4,520)	(4,095)
Multi-family servicing rights
Adverse changes to key assumptions on the carrying amount of the servicing rights
Prepayment rate (10% adverse change)	(481)	(491)
Prepayment rate (20% adverse change)	(947)	(965)
Default rate (10% adverse change)	(14)	(14)
Default rate (20% adverse change)	(28)	(29)
Discount rate (10% adverse change)	(2,305)	(2,320)
Discount rate (20% adverse change)	(4,496)	(4,524)
Cost of servicing (10% adverse change)	(2,590)	(2,587)
Cost of servicing (20% adverse change)	$ (5,180)	$ (5,173)