Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	$ 1,941	$ 1,635
Related Allowance	1,303	427
Fair Value, Measurements, Nonrecurring | Quoted Market Prices in an Active Market (Level 1)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans, net	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring | Models with Significant Observable Market Parameters (Level 2)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Impaired loans, net	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring | Models with Significant Unobservable Market Parameters (Level 3)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	1,941	1,635
Impaired loans, net	6,495	6,531
Total	8,436	8,166
Fair Value, Measurements, Nonrecurring | Total Carrying Value in the Consolidated Balance Sheet
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Other real estate owned	1,941	1,635
Impaired loans, net	6,495	6,531
Total	8,436	8,166
Related Allowance	$ 1,303	$ 427