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Securities - Summary of Investments in an Unrealized Loss Position that were Temporarily Impaired (Detail) - USD ($) $ in Thousands | Sep. 30, 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 |  | $ 52,580
Securities available for sale, 12 months or more - Fair Value | $ 6,022 | 14,462
Securities available for sale, Total - Fair Value | 6,022 | 67,042
Securities available for sale, Less than 12 months - Unrealized (Loss) |  | (479)
Securities available for sale, 12 months or more - Unrealized (Loss) | (62) | (414)
Total Unrealized (Loss) | (62) | (893)
Securities held to maturity, Less than 12 months - Fair Value |  | 35,843
Securities held to maturity, 12 months or more - Fair Value |  | 0
Securities held to maturity, Total - Fair Value |  | 35,843
Securities held to maturity, Less than 12 months - Unrealized (Loss) |  | (345)
Securities held to maturity, 12 months or more - Unrealized (Loss) |  | 0
Total Unrealized (Loss) |  | (345)
Total securities, Less than 12 months - Fair Value |  | 88,423
Total securities, 12 months or more - Fair Value | 6,022 | 14,462
Total securities, Total - Fair Value | 6,022 | 102,885
Total securities, Less than 12 months - Unrealized (Loss) |  | (824)
Total securities, 12 months or more - Unrealized (Loss) | (62) | (414)
Total Unrealized (Loss) | (62) | (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 |  | 50,185
Securities available for sale, 12 months or more - Fair Value | 6,022 | 13,409
Securities available for sale, Total - Fair Value | 6,022 | 63,594
Securities available for sale, Less than 12 months - Unrealized (Loss) |  | (464)
Securities available for sale, 12 months or more - Unrealized (Loss) | (62) | (379)
Total Unrealized (Loss) | $ (62) | (843)
Securities held to maturity, Less than 12 months - Fair Value |  | 32,791
Securities held to maturity, 12 months or more - Fair Value |  | 0
Securities held to maturity, Total - Fair Value |  | 32,791
Securities held to maturity, Less than 12 months - Unrealized (Loss) |  | (326)
Securities held to maturity, 12 months or more - Unrealized (Loss) |  | 0
Total Unrealized (Loss) |  | (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 |  | 2,395
Securities available for sale, 12 months or more - Fair Value |  | 1,053
Securities available for sale, Total - Fair Value |  | 3,448
Securities available for sale, Less than 12 months - Unrealized (Loss) |  | (15)
Securities available for sale, 12 months or more - Unrealized (Loss) |  | (35)
Total Unrealized (Loss) |  | (50)
Securities held to maturity, Less than 12 months - Fair Value |  | 3,052
Securities held to maturity, 12 months or more - Fair Value |  | 0
Securities held to maturity, Total - Fair Value |  | 3,052
Securities held to maturity, Less than 12 months - Unrealized (Loss) |  | (19)
Securities held to maturity, 12 months or more - Unrealized (Loss) |  | 0
Total Unrealized (Loss) |  | $ (19)

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