Securities - Summary of Investments in an Unrealized Loss Position that were Temporarily Impaired (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
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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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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