Annual report pursuant to Section 13 and 15(d)

Acquisitions, Goodwill and Other Intangible Assets - Additional Information (Detail)

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Acquisitions, Goodwill and Other Intangible Assets - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2018
USD ($)
Acquisition
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]      
Cash consideration $ 14,926,000 $ 0 $ 0
Contingent consideration and deferred payments in connection with acquisitions 3,727,000 0 $ 0
Contingent consideration $ 2,700,000    
Number of acquisitions | Acquisition 4    
Contingent consideration, maximum undiscounted payment $ 4,200,000    
Mortgage servicing assets, net 2,000,000    
Fair values of intangible assets 4,240,000 0  
Acquired working capital 100,000    
Goodwill 11,459,000 $ 0  
Other assets noncurrent 800,000    
Mortgage servicing rights [Member]      
Business Acquisition [Line Items]      
Mortgage servicing assets 2,100,000    
Mortgage servicing liabilities $ 100,000    
Minimum [Member] | Series of Individually Immaterial Business Acquisitions [Member]      
Business Acquisition [Line Items]      
Earn-out period for contingent consideration and deferred payments 1 year    
Maximum [Member] | Series of Individually Immaterial Business Acquisitions [Member]      
Business Acquisition [Line Items]      
Earn-out period for contingent consideration and deferred payments 7 years