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Securities - Summary of Amortized Costs and Fair Values of Securities (Detail) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Securities available for sale: |  |  |
Amortized Cost | $ 106,197 | $ 90,594 |
Gross Unrealized Gains | 39 | 153 |
Gross Unrealized (Losses) | (3,488) | (1,492) |
Fair Value | 102,748 | 89,255 |
Securities held to maturity: |  |  |
Amortized Cost | 44,239 | 48,208 |
Gross Unrealized Gains | 7 | 90 |
Gross Unrealized (Losses) | (1,539) | (596) |
Fair Value | 42,707 | 47,702 | [1]
Total securities, Amortized cost | 150,436 | 138,802 |
Total securities, Gross unrealized gains | 46 | 243 |
Total securities, Gross unrealized (losses) | (5,027) | (2,088) |
Total securities, Fair value | 145,455 | 136,957 |
U.S. agency and mortgage-backed securities |  |  |
Securities available for sale: |  |  |
Amortized Cost | 91,126 | 76,074 |
Gross Unrealized Gains | 14 | 67 |
Gross Unrealized (Losses) | (3,097) | (1,337) |
Fair Value | 88,043 | 74,804 |
Securities held to maturity: |  |  |
Amortized Cost | 28,233 | 32,149 |
Gross Unrealized Gains | 0 | 0 |
Gross Unrealized (Losses) | (1,208) | (551) |
Fair Value | 27,025 | 31,598 |
Obligations of states and political subdivisions |  |  |
Securities available for sale: |  |  |
Amortized Cost | 15,071 | 14,520 |
Gross Unrealized Gains | 25 | 86 |
Gross Unrealized (Losses) | (391) | (155) |
Fair Value | 14,705 | 14,451 |
Securities held to maturity: |  |  |
Amortized Cost | 14,506 | 14,559 |
Gross Unrealized Gains | 7 | 74 |
Gross Unrealized (Losses) | (320) | (45) |
Fair Value | 14,193 | 14,588 |
Corporate debt securities |  |  |
Securities held to maturity: |  |  |
Amortized Cost | 1,500 | 1,500 |
Gross Unrealized Gains | 0 | 16 |
Gross Unrealized (Losses) | (11) | 0 |
Fair Value | $ 1,489 | $ 1,516 |
[1] | Derived from audited consolidated financial statements.

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