Securities (Held to maturity securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 239,908	$ 253,550
Gross Unrealized Gains	8,422	12,460
Gross Unrealized Losses	(936)	(516)
Estimated Fair Value	247,394	265,494
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	239,908	253,550
Gross Unrealized Gains	8,422	12,460
Gross Unrealized Losses	(936)	(516)
Estimated Fair Value	$ 247,394	$ 265,494

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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