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Intangible Assets - Additional Information (Detail)
12 Months Ended
Dec. 31, 2017
USD ($)
Finite Lived Intangible Assets Net [Abstract]  
Amortization expense related to intangible assets $ 1,194,000
Estimated remaining useful life of intangible assets 2 months
Intangible assets, net $ 1,306,000
Impairment of intangible assets $ 0