Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Additional Information (Detail)

v3.8.0.1
Intangible Assets - Additional Information (Detail) - USD ($)
 12 Months Ended
Oct. 27, 2016
Aug. 31, 2014
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]          
Goodwill impairment     $ 0    
Intangible asset impairment charges     0 $ 0  
Core deposit intangible [Member]          
Finite-Lived Intangible Assets [Line Items]          
Total amortization expense for other intangible assets, including discontinued operations     $ 345,000 $ 326,000 $ 379,000
CBI Merger [Member]          
Finite-Lived Intangible Assets [Line Items]          
Goodwill $ 11,000,000        
CBI Merger [Member] | Core deposit intangible [Member]          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets acquired   $ 2,200,000      
CBI Merger [Member] | Third Party Originators Intangible [Member]          
Finite-Lived Intangible Assets [Line Items]          
Intangible assets acquired $ 483,000