Basis of presentation - Additional Information (Details) $ in Thousands	1 Months Ended	3 Months Ended
	May 01, 2020 USD ($)	Mar. 31, 2020 branch	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)
Class of Stock [Line Items]
Number of full-service branches | branch		73
Cumulative effect of new accounting principal			$ 25,018	$ 1,309
Retained earnings
Class of Stock [Line Items]
Cumulative effect of new accounting principal			$ 25,018	$ 1,309
Subsequent Event
Class of Stock [Line Items]
Deferred loans, principal balance	$ 791,253
Subsequent Event | SBA
Class of Stock [Line Items]
Loans processed	$ 325,803