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Nature of Banking Activities and Significant Accounting policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2015
USD ($)
Entity
Branch
Dec. 31, 2014
USD ($)
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Number of accounts included by parent company | Entity 6  
Recognition of other than temporary impairment on basis of credit loss description If there is no credit loss, there is no other-than-temporary impairment. If there is a credit loss, other-than-temporary impairment exists, and the credit loss must be recognized in net income and the remaining portion of impairment must be recognized in other comprehensive income.  
Gain (loss) on rate lock commitments $ 0  
Accrual status of loan 90 days  
Troubled debt restructurings (TDRs), amount $ 982,000 $ 1,900,000
Largest amount of tax benefit realized by taxing authority 50.00%  
Liability for unrecognized tax benefits $ 0 0
Advertising cost $ 400,000 $ 313,000
Bank of America [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Number of acquired branches | Branch 6  
Minimum [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Period of time between issuance of a loan commitment and closing and sale of the loan 30 days  
Company not considered value of impairment on individual consumer, residential and small commercial loans $ 250,000  
Management's policy on evaluation of impairment $ 250,000  
Minimum [Member] | Software [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Estimated useful lives of depreciation of premises and equipment 3 years  
Minimum [Member] | Core Deposits [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Intangible assets, estimated useful lives 6 years  
Minimum [Member] | Premises and Equipment [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Estimated useful lives of depreciation of premises and equipment 3 years  
Maximum [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Period of time between issuance of a loan commitment and closing and sale of the loan 60 days  
Maximum [Member] | Software [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Estimated useful lives of depreciation of premises and equipment 7 years  
Maximum [Member] | Core Deposits [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Intangible assets, estimated useful lives 9 years  
Maximum [Member] | Premises and Equipment [Member]    
Nature Of Banking Activities And Significant Accounting Policies [Line Items]    
Estimated useful lives of depreciation of premises and equipment 40 years