Investment Securities - Summary of Unrealized Losses of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Securities with losses under 12 months, Fair Value	$ 28,567	$ 19,478
Held-to-maturity, Securities with losses under 12 months, Gross Unrealized Loss	375	117
Held-to-maturity, Securities with losses over 12 months, Fair Value	20,578	12,090
Held-to-maturity, Securities with losses over 12 months, Gross Unrealized Loss	1,020	451
Held-to-maturity, Total, Fair Value	49,145	31,568
Held-to-maturity, Total, Gross Unrealized Loss	1,395	568
Obligations of state and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Securities with losses under 12 months, Fair Value	12,645	6,340
Held-to-maturity, Securities with losses under 12 months, Gross Unrealized Loss	149	22
Held-to-maturity, Securities with losses over 12 months, Fair Value	0	0
Held-to-maturity, Securities with losses over 12 months, Gross Unrealized Loss	0	0
Held-to-maturity, Total, Fair Value	12,645	6,340
Held-to-maturity, Total, Gross Unrealized Loss	149	22
Collateralized Mortgage Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Securities with losses under 12 months, Fair Value	15,922	13,138
Held-to-maturity, Securities with losses under 12 months, Gross Unrealized Loss	226	95
Held-to-maturity, Securities with losses over 12 months, Fair Value	20,578	12,090
Held-to-maturity, Securities with losses over 12 months, Gross Unrealized Loss	1,020	451
Held-to-maturity, Total, Fair Value	36,500	25,228
Held-to-maturity, Total, Gross Unrealized Loss	$ 1,246	$ 546

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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

+ References

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-Publisher FASB
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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

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