Investment Securities (Details 3) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Taxable interest	$ 14,599	$ 13,724	$ 12,166
Non-taxable interest	11,107	11,429	10,381
Dividend income	432	559	492
Total interest income on investment securities	$ 26,138	$ 25,712	$ 23,039

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.2)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

+ References

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Amount of dividend income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(a),(b))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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