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Intangible Asset - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]      
Intangible asset estimated weighted- average remaining useful life 11 years 7 months 6 days    
Amortization of intangible asset $ 646 $ 646 $ 645