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Securities - Summary of Amortized Cost and Fair Values of Securities Held-to-maturity (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Schedule Of Held To Maturity Securities [Line Items] |  |
Held-to-maturity Securities, Amortized Cost | $ 117,163 | $ 138,846
Held-to-maturity Securities, Gross Unrealized Gains | 450 | 190
Held-to-maturity Securities, Gross Unrealized Losses | (336) | (954)
Securities held-to-maturity, fair value | 117,277 | 138,082
Obligations of States, Municipalities, and Political Subdivisions |  |
Schedule Of Held To Maturity Securities [Line Items] |  |
Held-to-maturity Securities, Amortized Cost | 24,030 | 24,878
Held-to-maturity Securities, Gross Unrealized Gains | 197 | 105
Held-to-maturity Securities, Gross Unrealized Losses | (82) | (229)
Securities held-to-maturity, fair value | 24,145 | 24,754
Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Held To Maturity Securities [Line Items] |  |
Held-to-maturity Securities, Amortized Cost | 53,731 | 67,692
Held-to-maturity Securities, Gross Unrealized Gains | 79 | 35
Held-to-maturity Securities, Gross Unrealized Losses | (203) | (283)
Securities held-to-maturity, fair value | 53,607 | 67,444
Non-Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Held To Maturity Securities [Line Items] |  |
Held-to-maturity Securities, Amortized Cost | 39,402 | 46,276
Held-to-maturity Securities, Gross Unrealized Gains | 174 | 50
Held-to-maturity Securities, Gross Unrealized Losses | (51) | (442)
Securities held-to-maturity, fair value | $ 39,525 | $ 45,884

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- Definition Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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- Definition Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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