Securities - Summary of Amortized Cost and Fair Values of Securities Held-to-maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule Of Held To Maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost	$ 102,683	$ 117,163
Held-to-maturity Securities, Gross Unrealized Gains	54	450
Held-to-maturity Securities, Gross Unrealized Losses	(2,804)	(336)
Securities held-to-maturity, fair value	99,933	117,277
Obligations of States, Municipalities, and Political Subdivisions
Schedule Of Held To Maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost	23,885	24,030
Held-to-maturity Securities, Gross Unrealized Gains	14	197
Held-to-maturity Securities, Gross Unrealized Losses	(545)	(82)
Securities held-to-maturity, fair value	23,354	24,145
Agency, Residential Mortgage-Backed Securities
Schedule Of Held To Maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost	42,668	53,731
Held-to-maturity Securities, Gross Unrealized Gains	40	79
Held-to-maturity Securities, Gross Unrealized Losses	(948)	(203)
Securities held-to-maturity, fair value	41,760	53,607
Non-Agency, Residential Mortgage-Backed Securities
Schedule Of Held To Maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost	36,130	39,402
Held-to-maturity Securities, Gross Unrealized Gains		174
Held-to-maturity Securities, Gross Unrealized Losses	(1,311)	(51)
Securities held-to-maturity, fair value	$ 34,819	$ 39,525

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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-Publisher FASB
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-Topic 320
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-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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