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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule Of Income Taxes [Line Items]                      
Income tax expense $ 4,014 $ 4,020 $ 3,668 $ 3,215 $ 4,969 $ 3,987 $ 3,316 $ 2,502 $ 14,917 $ 14,774 $ 9,137
Federal income tax rate                 35.00% 35.00% 35.00%
Cumulative pre-tax book income position period                 3 years 3 years  
Taxable income generation period                 2 years    
State net operating loss carryforward $ 1,200       $ 600       $ 1,200 $ 600  
Minimum [Member]                      
Schedule Of Income Taxes [Line Items]                      
State net operating loss carryforwards expiration period                 2030    
Maximum [Member]                      
Schedule Of Income Taxes [Line Items]                      
State net operating loss carryforwards expiration period                 2035