Other assets and other liabilities - Summary of Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Assets And Other Liabilities [Abstract]
Deferred compensation	$ 1,718	$ 3,836
Accrued payroll	16,517	8,026
Mortgage servicing escrows	4,526	4,441
Mortgage buyback reserve	3,529	3,273
Accrued interest	6,465	5,015
Derivatives	17,933	11,637
Deferred tax liability	20,490	16,663
FHLB lender risk account guaranty	5,546	2,646
Other liabilities	10,730	9,877
Total other liabilities	$ 87,454	$ 65,414