Regulatory Matters - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Periodic increase of capital conservation buffer	0.625%
Total risk-based capital ratio, Actual Ratio	18.45%	16.97%
Tier1 Capital (to Risk-Weighted Assets), Actual Ratio	17.30%	15.90%
Common Tier1 Capital (to Risk-Weighted Assets), Actual Ratio	17.30%	15.90%
Tier1 Leverage ratio, Actual Ratio	10.71%	9.96%
Required tangible net assets	$ 2,000,000
Tangible net assets, total	14,300,000
Subsidiary bank's reserve balance	$ 4,340,000	$ 17,725,000
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	0.625%
Maximum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%