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Securities - Summary of Investments in an Unrealized Loss Position that were Temporarily Impaired (Detail) - USD ($) $ in Thousands | Mar. 31, 2017 | Dec. 31, 2016
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Schedule of Available-for-sale Securities [Line Items] |  |
Securities available for sale, Less than 12 months - Fair Value | $ 55,987 | $ 66,073
Securities available for sale, 12 months or more - Fair Value | 5,190 | 5,499
Securities available for sale, Total - Fair Value | 61,177 | 71,572
Securities available for sale, Less than 12 months - Unrealized (Loss) | (933) | (1,429)
Securities available for sale, 12 months or more - Unrealized (Loss) | (188) | (208)
Total Unrealized (Loss) | (1,121) | (1,637)
Securities held to maturity, Less than 12 months - Fair Value | 37,022 | 48,980
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 37,022 | 48,980
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (460) | (708)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (460) | (708)
Total securities, Less than 12 months - Fair Value | 93,009 | 115,053
Total securities, 12 months or more - Fair Value | 5,190 | 5,499
Total securities, Total - Fair Value | 98,199 | 120,552
Total securities, Less than 12 months - Unrealized (Loss) | (1,393) | (2,137)
Total securities, 12 months or more - Unrealized (Loss) | (188) | (208)
Total Unrealized (Loss) | (1,581) | (2,345)
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 | 52,461 | 60,943
Securities available for sale, 12 months or more - Fair Value | 5,190 | 5,499
Securities available for sale, Total - Fair Value | 57,651 | 66,442
Securities available for sale, Less than 12 months - Unrealized (Loss) | (797) | (1,249)
Securities available for sale, 12 months or more - Unrealized (Loss) | (188) | (208)
Total Unrealized (Loss) | (985) | (1,457)
Securities held to maturity, Less than 12 months - Fair Value | 26,783 | 34,770
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 26,783 | 34,770
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (351) | (483)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (351) | (483)
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 | 3,526 | 5,130
Securities available for sale, Total - Fair Value | 3,526 | 5,130
Securities available for sale, Less than 12 months - Unrealized (Loss) | (136) | (180)
Total Unrealized (Loss) | (136) | (180)
Securities held to maturity, Less than 12 months - Fair Value | 8,755 | 12,724
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 8,755 | 12,724
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (93) | (211)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | (93) | (211)
Corporate Debt Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Securities held to maturity, Less than 12 months - Fair Value | 1,484 | 1,486
Securities held to maturity, 12 months or more - Fair Value | 0 | 0
Securities held to maturity, Total - Fair Value | 1,484 | 1,486
Securities held to maturity, Less than 12 months - Unrealized (Loss) | (16) | (14)
Securities held to maturity, 12 months or more - Unrealized (Loss) | 0 | 0
Total Unrealized (Loss) | $ (16) | $ (14)

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