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Investment Securities Held to Maturity Securities by Type (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
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Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | $ 389,621 | $ 422,096
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 5 | 345
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (15,693) | (4,192)
Securities held to maturity, fair value | 373,933 | 418,249
US Government Agencies Residential Mortgage-backed Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 3,663 | 3,925
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (156) | (14)
Securities held to maturity, fair value | 3,507 | 3,911
US Government Agency Debt Securities Commercial [Domain] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 55,726 | 58,249
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (2,742) | (1,394)
Securities held to maturity, fair value | 52,984 | 56,855
Residential Mortgage Backed Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 273,972 | 305,126
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 10
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (11,468) | (2,552)
Securities held to maturity, fair value | 262,504 | 302,584
Obligations of U.S. Government-Sponsored Enterprises - Mortgage-Backed Securities - Commercial [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 13,413 | 14,056
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (427) | (71)
Securities held to maturity, fair value | 12,986 | 13,985
Obligations of States and Political Subdivisions [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 42,447 | 40,540
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 5 | 335
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (895) | (161)
Securities held to maturity, fair value | 41,557 | 40,714
Debt Security, Government, Non-US [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 400 | 200
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (5) | 0
Securities held to maturity, fair value | $ 395 | $ 200

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- Definition Amount of investment in debt security measured at amortized cost (held-to-maturity). + References 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 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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- Definition 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 -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 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 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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