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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
Goodwill And Other Intangibles [Line Items]      
Amortization expenses of other intangible assets $ 13,700,000 $ 13,400,000 $ 14,200,000
Amortization of intangible assets, weighted average period, years 12 years    
Annual impairment of goodwill $ 0 0 0
Intangible asset impairment charge 0 $ 0 $ 0
Annually      
Goodwill And Other Intangibles [Line Items]      
Amortization expenses of other intangible assets $ 14,500,000