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Investment Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands | Sep. 30, 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 | $ 164,222 | $ 151,032
Held to maturity, Fair Value | 158,106 | 151,032
Held-to-maturity, Gross Unrealized Gains | 160 | 619
Held-to-maturity, Gross Unrealized Losses | (6,276) | (619)
Total | 416,732 | 334,285
Available-for-sale, at fair value | 405,571 | 332,467
Available-for-sale, Gross Unrealized Gains | 88 | 574
Available-for-sale, Gross Unrealized Losses | (11,249) | (2,392)
Total investment securities, Amortized Cost | 580,954 | 485,317
Total investment securities, Fair Value | 563,677 | 483,499
Total investment securities, Gross Unrealized Gains | 248 | 1,193
Total investment securities, Gross Unrealized Losses | (17,525) | (3,011)
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 | 91,237 | 100,376
Held to maturity, Fair Value | 86,962 | 100,096
Held-to-maturity, Gross Unrealized Gains | 0 | 234
Held-to-maturity, Gross Unrealized Losses | (4,275) | (514)
Total | 93,096 | 65,559
Available-for-sale, at fair value | 90,484 | 65,262
Available-for-sale, Gross Unrealized Gains | 20 | 126
Available-for-sale, Gross Unrealized Losses | (2,632) | (423)
SBA-backed securities |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 8,723 | 0
Held to maturity, Fair Value | 8,489 | 0
Held-to-maturity, Gross Unrealized Gains | 0 | 0
Held-to-maturity, Gross Unrealized Losses | (234) | 0
Total | 41,074 | 25,979
Available-for-sale, at fair value | 40,181 | 25,982
Available-for-sale, Gross Unrealized Gains | 0 | 58
Available-for-sale, Gross Unrealized Losses | (893) | (55)
CMOs issued by FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 11,646 | 0
Held to maturity, Fair Value | 11,254 | 0
Held-to-maturity, Gross Unrealized Gains | 0 | 0
Held-to-maturity, Gross Unrealized Losses | (392) | 0
Total | 19,914 | 35,340
Available-for-sale, at fair value | 19,356 | 35,125
Available-for-sale, Gross Unrealized Gains | 4 | 33
Available-for-sale, Gross Unrealized Losses | (562) | (248)
CMOs issued by FHLMC |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 34,169 | 31,010
Held to maturity, Fair Value | 32,868 | 30,938
Held-to-maturity, Gross Unrealized Gains | 0 | 2
Held-to-maturity, Gross Unrealized Losses | (1,301) | (74)
Total | 128,848 | 70,514
Available-for-sale, at fair value | 124,930 | 69,889
Available-for-sale, Gross Unrealized Gains | 1 | 3
Available-for-sale, Gross Unrealized Losses | (3,919) | (628)
CMOs issued by GNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 3,734 | 0
Held to maturity, Fair Value | 3,694 | 0
Held-to-maturity, Gross Unrealized Gains | 0 | 0
Held-to-maturity, Gross Unrealized Losses | (40) | 0
Total | 11,938 | 17,953
Available-for-sale, at fair value | 11,450 | 17,785
Available-for-sale, Gross Unrealized Gains | 0 | 26
Available-for-sale, Gross Unrealized Losses | (488) | (194)
Debentures of government- sponsored agencies |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Total | 43,470 | 12,940
Available-for-sale, at fair value | 42,914 | 12,938
Available-for-sale, Gross Unrealized Gains | 0 | 3
Available-for-sale, Gross Unrealized Losses | (556) | (5)
Privately issued CMOs |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Total | 367 | 1,432
Available-for-sale, at fair value | 370 | 1,431
Available-for-sale, Gross Unrealized Gains | 3 | 1
Available-for-sale, Gross Unrealized Losses | 0 | (2)
Obligations of state and political subdivisions |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, Amortized Cost | 14,713 | 19,646
Held to maturity, Fair Value | 14,839 | 19,998
Held-to-maturity, Gross Unrealized Gains | 160 | 383
Held-to-maturity, Gross Unrealized Losses | (34) | (31)
Total | 75,519 | 98,027
Available-for-sale, at fair value | 73,373 | 97,491
Available-for-sale, Gross Unrealized Gains | 41 | 298
Available-for-sale, Gross Unrealized Losses | (2,187) | (834)
Corporate bonds |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Total | 2,506 | 6,541
Available-for-sale, at fair value | 2,513 | 6,564
Available-for-sale, Gross Unrealized Gains | 19 | 26
Available-for-sale, Gross Unrealized Losses | $ (12) | $ (3)

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