Securities Available for Sale - Amortized cost and fair values of securities available for sale at by contractual maturity (Details 4) $ in Thousands	Sep. 30, 2018 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in less than one year	$ 21,592
Amortized Cost, Due in one year through five years	157,636
Amortized Cost, Due after five years through ten years	95,324
Amortized Cost, Due after ten years	6,969
Single maturity date, Amortized Cost	281,521
Amortized Cost	421,948
Fair Value, Due in less than one year	21,559
Fair Value, Due in one year through five years	154,294
Fair Value, Due after five years through ten years	92,078
Fair Value, Due after ten years	7,135
Single maturity date, Fair value	275,066
Fair Value	410,911
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	140,427
Fair Value	$ 135,845

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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