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Securities - Summary of Amortized Costs and Fair Values of Securities (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Securities available for sale: |  |
Amortized Cost | $ 90,594 | $ 96,106
Gross Unrealized Gains | 153 | 333
Gross Unrealized (Losses) | (1,492) | (1,637)
Fair Value | 89,255 | 94,802
Securities held to maturity: |  |
Amortized Cost | 48,208 | 53,398
Gross Unrealized Gains | 90 | 19
Gross Unrealized (Losses) | (596) | (708)
Fair Value | 47,702 | 52,709
Total securities, Amortized cost | 138,802 | 149,504
Total securities, Gross unrealized gains | 243 | 352
Total securities, Gross unrealized (losses) | (2,088) | (2,345)
Total securities, Fair value | 136,957 | 147,511
U.S. agency and mortgage-backed securities |  |
Securities available for sale: |  |
Amortized Cost | 76,074 | 81,451
Gross Unrealized Gains | 67 | 177
Gross Unrealized (Losses) | (1,337) | (1,457)
Fair Value | 74,804 | 80,171
Securities held to maturity: |  |
Amortized Cost | 32,149 | 37,269
Gross Unrealized Gains | 0 | 1
Gross Unrealized (Losses) | (551) | (483)
Fair Value | 31,598 | 36,787
Obligations of states and political subdivisions |  |
Securities available for sale: |  |
Amortized Cost | 14,520 | 14,654
Gross Unrealized Gains | 86 | 146
Gross Unrealized (Losses) | (155) | (180)
Fair Value | 14,451 | 14,620
Securities held to maturity: |  |
Amortized Cost | 14,559 | 14,629
Gross Unrealized Gains | 74 | 18
Gross Unrealized (Losses) | (45) | (211)
Fair Value | 14,588 | 14,436
Corporate equity securities |  |
Securities available for sale: |  |
Amortized Cost |  | 1
Gross Unrealized Gains |  | 10
Gross Unrealized (Losses) |  | 0
Fair Value |  | 11
Corporate debt securities |  |
Securities held to maturity: |  |
Amortized Cost | 1,500 | 1,500
Gross Unrealized Gains | 16 | 0
Gross Unrealized (Losses) | 0 | (14)
Fair Value | $ 1,516 | $ 1,486

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