Goodwill and Intangible Assets Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Goodwill not subject to amortization (effective 1/1/02)	$ 63,910	$ 63,910
Total Goodwill And Intangible Assets, Gross Carrying Value	90,518	90,518
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	20,999	20,533
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	19,862	19,862
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	11,893	11,473
Customer Lists [Member]
Goodwill and Intangible Assets Gross Carrying Value [Abstract]
Finite-Lived Intangible Assets, Gross	3,731	3,731
Goodwill and Intangible Assets Accumulated Amortization [Abstract]
Finite-Lived Intangible Assets, Accumulated Amortization	$ 2,331	$ 2,285