Securities - Summary of Gross Unrealized Losses and Fair Value of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Total	$ 249	$ 597
Gross Unrealized Losses, Total	582	1,316
Gross Unrealized Losses, Less Than 12 Months	300	1,583
Fair Value, Less Than 12 Months	32,636	67,186
Gross Unrealized Losses, 12 Months Or More	531	330
Fair Value, 12 Months Or More	21,417	6,776
Gross Unrealized Losses, Total	831	1,913
Fair Value, Total	54,053	73,962
U.S. Treasury Security [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	1
Fair Value, Less Than 12 Months	998
Gross Unrealized Losses, Total	1
Fair Value, Total	998
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Less Than 12 Months	32	396
Held-to-maturity, Fair Value, Less Than 12 Months	3,966	8,602
Held-to-maturity, Gross Unrealized Losses, 12 Months Or More	121
Held-to-maturity, Fair Value, 12 Months Or More	4,879
Held-to-maturity, Gross Unrealized Losses, Total	153	396
Held-to-maturity, Fair Value, Total	8,845	8,602
Gross Unrealized Losses, Less Than 12 Months	10	98
Fair Value, Less Than 12 Months	3,840	6,402
Gross Unrealized Losses, 12 Months Or More	40
Fair Value, 12 Months Or More	4,460
Gross Unrealized Losses, Total	50	98
Fair Value, Total	8,300	6,402
Mortgage-Backed Securities of Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Less Than 12 Months	3	28
Held-to-maturity, Fair Value, Less Than 12 Months	2,011	2,018
Held-to-maturity, Gross Unrealized Losses, 12 Months Or More	93	173
Held-to-maturity, Fair Value, 12 Months Or More	3,274	3,621
Held-to-maturity, Gross Unrealized Losses, Total	96	201
Held-to-maturity, Fair Value, Total	5,285	5,639
Gross Unrealized Losses, Less Than 12 Months	245	589
Fair Value, Less Than 12 Months	20,128	27,243
Gross Unrealized Losses, 12 Months Or More	41
Fair Value, 12 Months Or More	2,316
Gross Unrealized Losses, Total	286	589
Fair Value, Total	22,444	27,243
Asset-Backed Securities of Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, 12 Months Or More	4	46
Fair Value, 12 Months Or More	1,194	1,266
Gross Unrealized Losses, Total	4	46
Fair Value, Total	1,194	1,266
State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	9	439
Fair Value, Less Than 12 Months	1,693	19,328
Gross Unrealized Losses, 12 Months Or More	65
Fair Value, 12 Months Or More	2,961
Gross Unrealized Losses, Total	74	439
Fair Value, Total	4,654	19,328
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months		33
Fair Value, Less Than 12 Months		3,593
Gross Unrealized Losses, 12 Months Or More	167	111
Fair Value, 12 Months Or More	2,333	1,889
Gross Unrealized Losses, Total	167	144
Fair Value, Total	$ 2,333	$ 5,482