Goodwill and other intangible assets - Components of other intangible assets subject to amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets
Gross amount	$ 39,695	$ 39,695
Finite Lived Intangible Assets Accumulated Amortization	24,444	23,393
Finite-Lived Intangible Assets, Net	15,251	16,302
Core deposits
Finite-Lived Intangible Assets
Core deposits - Gross	12,810	12,810
Finite Lived Intangible Assets Accumulated Amortization	7,793	7,473
Finite-Lived Intangible Assets, Net	5,017	5,337
Other customer relationship
Finite-Lived Intangible Assets
Customer relationships - Gross	26,397	26,397
Finite Lived Intangible Assets Accumulated Amortization	16,390	15,684
Finite-Lived Intangible Assets, Net	10,007	10,713
Trademarks
Finite-Lived Intangible Assets
Gross amount	488	488
Finite Lived Intangible Assets Accumulated Amortization	261	236
Finite-Lived Intangible Assets, Net	$ 227	$ 252