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Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Goodwill And Intangible Assets [Line Items]      
Amortization expense related to finite lived intangible assets $ 5,263 $ 5,213 $ 5,315