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Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]          
Accumulated impairment losses $ 0   $ 0   $ 0
Amortization expense on intangible assets $ 6,600,000 $ 911,000 $ 16,300,000 $ 2,700,000