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Intangible Assets - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]      
Amortization expense for intangible assets $ 1,900,000 $ 800,000 $ 1,400,000
Impairment losses 0 0  
Goodwill acquired during the year $ 0 $ 0