Note Goodwill and other intangible assets (Components of other intangible assets subject to amortization) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets
Gross Amount	$ 72,627	$ 72,627
Finite Lived Intangible Assets Accumulated Amortization	54,270	51,958
Finite-Lived Intangible Assets, Net	18,357	20,669
Core deposits
Finite-Lived Intangible Assets
Core deposits - Gross	37,224	37,224
Finite Lived Intangible Assets Accumulated Amortization	27,000	26,070
Finite-Lived Intangible Assets, Net	10,224	11,154
Other customer relationship
Finite-Lived Intangible Assets
Customer relationships - Gross	34,915	34,915
Finite Lived Intangible Assets Accumulated Amortization	27,205	25,847
Finite-Lived Intangible Assets, Net	7,710	9,068
Trademarks
Finite-Lived Intangible Assets
Gross Amount	488	488
Finite Lived Intangible Assets Accumulated Amortization	65	41
Finite-Lived Intangible Assets, Net	$ 423	$ 447