Securities - Summary of Gross Unrealized Losses and Fair Value of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Total	$ 727	$ 378
Gross Unrealized Losses, Total	2,083	948
Gross Unrealized Losses, Less Than 12 Months	947	258
Fair Value, Less Than 12 Months	58,086	37,484
Gross Unrealized Losses, 12 Months Or More	1,863	1,068
Fair Value, 12 Months Or More	39,340	37,697
Gross Unrealized Losses, Total	2,810	1,326
Fair Value, Total	97,426	75,181
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Less Than 12 Months	44	15
Held-to-maturity, Fair Value, Less Than 12 Months	1,956	1,985
Held-to-maturity, Gross Unrealized Losses, 12 Months Or More	408	213
Held-to-maturity, Fair Value, 12 Months Or More	6,591	6,785
Held-to-maturity, Gross Unrealized Losses, Total	452	228
Held-to-maturity, Fair Value, Total	8,547	8,770
Gross Unrealized Losses, Less Than 12 Months	56	46
Fair Value, Less Than 12 Months	1,944	3,804
Gross Unrealized Losses, 12 Months Or More	203	75
Fair Value, 12 Months Or More	6,147	4,425
Gross Unrealized Losses, Total	259	121
Fair Value, Total	8,091	8,229
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	142	18
Held-to-maturity, Fair Value, Less Than 12 Months	7,325	1,818
Held-to-maturity, Gross Unrealized Losses, 12 Months Or More	133	127
Held-to-maturity, Fair Value, 12 Months Or More	2,846	3,116
Held-to-maturity, Gross Unrealized Losses, Total	275	145
Held-to-maturity, Fair Value, Total	10,171	4,934
Gross Unrealized Losses, Less Than 12 Months	460	145
Fair Value, Less Than 12 Months	25,360	16,872
Gross Unrealized Losses, 12 Months Or More	773	436
Fair Value, 12 Months Or More	17,787	17,259
Gross Unrealized Losses, Total	1,233	581
Fair Value, Total	43,147	34,131
State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Gross Unrealized Losses, Less Than 12 Months		5
Held-to-maturity, Fair Value, Less Than 12 Months		4,695
Held-to-maturity, Gross Unrealized Losses, Total		5
Held-to-maturity, Fair Value, Total		4,695
Gross Unrealized Losses, Less Than 12 Months	177	26
Fair Value, Less Than 12 Months	12,944	4,400
Gross Unrealized Losses, 12 Months Or More	172	77
Fair Value, 12 Months Or More	3,643	3,752
Gross Unrealized Losses, Total	349	103
Fair Value, Total	16,587	8,152
U.S. Treasury Security [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	1	1
Fair Value, Less Than 12 Months	992	998
Gross Unrealized Losses, Total	1	1
Fair Value, Total	992	998
Asset-Backed Securities of Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	3
Fair Value, Less Than 12 Months	1,101
Gross Unrealized Losses, Total	3
Fair Value, Total	1,101
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than 12 Months	64	2
Fair Value, Less Than 12 Months	6,464	2,912
Gross Unrealized Losses, 12 Months Or More	174	140
Fair Value, 12 Months Or More	2,326	2,360
Gross Unrealized Losses, Total	238	142
Fair Value, Total	$ 8,790	$ 5,272