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Investment Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
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Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | $ 149,013 | $ 151,032
Held to maturity, Fair Value | 145,818 | 151,032
Held-to-maturity, Gross Unrealized Gains | 291 | 619
Held-to-maturity, Gross Unrealized Losses | (3,486) | (619)
Available-for-sale, Amortized Cost | 431,871 | 334,285
Available-for-sale, at fair value | 423,882 | 332,467
Available-for-sale, Gross Unrealized Gains | 239 | 574
Available-for-sale, Gross Unrealized Losses | (8,228) | (2,392)
Total investment securities, Amortized Cost | 580,884 | 485,317
Total investment securities, Fair Value | 569,700 | 483,499
Total investment securities, Gross Unrealized Gains | 530 | 1,193
Total investment securities, Gross Unrealized Losses | (11,714) | (3,011)
MBS pass-through securities issued by FHLMC and FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 93,915 | 65,559
Available-for-sale, at fair value | 92,029 | 65,262
Available-for-sale, Gross Unrealized Gains | 22 | 126
Available-for-sale, Gross Unrealized Losses | (1,908) | (423)
SBA-backed securities |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 33,809 | 25,979
Available-for-sale, at fair value | 33,538 | 25,982
Available-for-sale, Gross Unrealized Gains | 8 | 58
Available-for-sale, Gross Unrealized Losses | (279) | (55)
CMOs issued by FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 34,210 | 35,340
Available-for-sale, at fair value | 33,613 | 35,125
Available-for-sale, Gross Unrealized Gains | 9 | 33
Available-for-sale, Gross Unrealized Losses | (606) | (248)
CMOs issued by FHLMC |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 123,007 | 70,514
Available-for-sale, at fair value | 120,374 | 69,889
Available-for-sale, Gross Unrealized Gains | 60 | 3
Available-for-sale, Gross Unrealized Losses | (2,693) | (628)
CMOs issued by GNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 17,173 | 17,953
Available-for-sale, at fair value | 16,650 | 17,785
Available-for-sale, Gross Unrealized Gains | 5 | 26
Available-for-sale, Gross Unrealized Losses | (528) | (194)
Debentures of government- sponsored agencies |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 27,446 | 12,940
Available-for-sale, at fair value | 27,336 | 12,938
Available-for-sale, Gross Unrealized Gains | 6 | 3
Available-for-sale, Gross Unrealized Losses | (116) | (5)
Privately issued CMOs |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 1,389 | 1,432
Available-for-sale, at fair value | 1,390 | 1,431
Available-for-sale, Gross Unrealized Gains | 3 | 1
Available-for-sale, Gross Unrealized Losses | (2) | (2)
Obligations of state and political subdivisions |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 95,395 | 98,027
Available-for-sale, at fair value | 93,414 | 97,491
Available-for-sale, Gross Unrealized Gains | 99 | 298
Available-for-sale, Gross Unrealized Losses | (2,080) | (834)
Corporate bonds |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Available-for-sale, Amortized Cost | 5,527 | 6,541
Available-for-sale, at fair value | 5,538 | 6,564
Available-for-sale, Gross Unrealized Gains | 27 | 26
Available-for-sale, Gross Unrealized Losses | (16) | (3)
Obligations of state and political subdivisions |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 19,599 | 19,646
Held to maturity, Fair Value | 19,857 | 19,998
Held-to-maturity, Gross Unrealized Gains | 278 | 383
Held-to-maturity, Gross Unrealized Losses | (20) | (31)
MBS pass-through securities issued by FHLMC and FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 97,222 | 100,376
Held to maturity, Fair Value | 94,735 | 100,096
Held-to-maturity, Gross Unrealized Gains | 12 | 234
Held-to-maturity, Gross Unrealized Losses | (2,499) | (514)
CMOs issued by FHLMC |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 32,192 | 31,010
Held to maturity, Fair Value | 31,226 | 30,938
Held-to-maturity, Gross Unrealized Gains | 1 | 2
Held-to-maturity, Gross Unrealized Losses | $ (967) | $ (74)

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