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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]      
Amortization expense $ 6,300,000 $ 6,200,000 $ 3,300,000
Impairment of Intangible Assets (Excluding Goodwill) 400,000 2,700,000  
Capitalized software development costs      
Finite-Lived Intangible Assets [Line Items]      
Amortization expense $ 900,000 $ 300,000 $ 25,000