Goodwill and Intangible Assets Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Goodwill not subject to amortization (effective 1/1/02)	$ 108,757	$ 109,037
Total Goodwill And Intangible Assets, Gross Carrying Value	160,156	160,436
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	24,738	23,440
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	14,997	14,017
Customer Lists [Member]
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Finite-Lived Intangible Assets, Gross	16,029	16,029
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 2,966	$ 2,648