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Securities - Summary of Investments in an Unrealized Loss Position that were Temporarily Impaired (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
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Schedule of Available-for-sale Securities [Line Items] |  |
Securities available for sale, Less than 12 months - Fair Value | $ 66,073 | $ 52,580
Securities available for sale, 12 months or more - Fair Value | 5,499 | 14,462
Securities available for sale, Total - Fair Value | 71,572 | 67,042
Securities available for sale, Less than 12 months - Unrealized (Loss) | (1,429) | (479)
Securities available for sale, 12 months or more - Unrealized (Loss) | (208) | (414)
Total Unrealized (Loss) | (1,637) | (893)
Securities held to maturity, Less than 12 months - Fair Value | 48,980 | 35,843
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 48,980 | 35,843
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (708) | (345)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (708) | (345)
Total securities, Less than 12 months - Fair Value | 115,053 | 88,423
Total securities, 12 months or more - Fair Value | 5,499 | 14,462
Total securities, Total - Fair Value | 120,552 | 102,885
Total securities, Less than 12 months - Unrealized (Loss) | (2,137) | (824)
Total securities, 12 months or more - Unrealized (Loss) | (208) | (414)
Total Unrealized (Loss) | (2,345) | (1,238)
U.S. Agency and Mortgage-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Securities available for sale, Less than 12 months - Fair Value | 60,943 | 50,185
Securities available for sale, 12 months or more - Fair Value | 5,499 | 13,409
Securities available for sale, Total - Fair Value | 66,442 | 63,594
Securities available for sale, Less than 12 months - Unrealized (Loss) | (1,249) | (464)
Securities available for sale, 12 months or more - Unrealized (Loss) | (208) | (379)
Total Unrealized (Loss) | (1,457) | (843)
Securities held to maturity, Less than 12 months - Fair Value | 34,770 | 32,791
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 34,770 | 32,791
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (483) | (326)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (483) | (326)
Obligations of States and Political Subdivisions [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Securities available for sale, Less than 12 months - Fair Value | 5,130 | 2,395
Securities available for sale, 12 months or more - Fair Value |  | 1,053
Securities available for sale, Total - Fair Value | 5,130 | 3,448
Securities available for sale, Less than 12 months - Unrealized (Loss) | (180) | (15)
Securities available for sale, 12 months or more - Unrealized (Loss) |  | (35)
Total Unrealized (Loss) | (180) | (50)
Securities held to maturity, Less than 12 months - Fair Value | 12,724 | 3,052
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 12,724 | 3,052
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (211) | (19)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (211) | $ (19)
Corporate Debt Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Securities held to maturity, Less than 12 months - Fair Value | 1,486 |
Securities held to maturity, 12 months or more - Fair Value | 0 |
Securities held to maturity, Total - Fair Value | 1,486 |
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (14) |
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 |
Total Unrealized (Loss) | $ (14) |

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