Goodwill and Intangible Assets Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Goodwill not subject to amortization (effective 1/1/02)	$ 108,752	$ 108,752
Total Goodwill And Intangible Assets, Gross Carrying Value	160,511	160,251
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Goodwill not subject to amortization (effective 1/1/02)	3,760	3,760
Total Goodwill and Intangible Assets, Accumulated Amortization	29,608	28,438
Intangibles from branch acquisition
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Finite-Lived Intangible Assets, Gross	3,015	3,015
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	3,015	3,015
Core Deposits [Member]
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Finite-Lived Intangible Assets, Gross	32,355	32,355
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	18,589	17,746
Customer Lists [Member]
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Finite-Lived Intangible Assets, Gross	16,389	16,129
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 4,244	$ 3,917