Quarterly report pursuant to Section 13 or 15(d)

Impairment of Long-Lived Assets - Additional Information (Detail)

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Impairment of Long-Lived Assets - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Mar. 31, 2017
Sep. 30, 2018
Sep. 30, 2017
Impairment Of Long Lived Assets [Line Items]          
Impairment of long-lived assets       $ 0  
Amortization of intangibles $ 1,600,000 $ 1,100,000   $ 4,600,000 $ 3,400,000
Adjustment To Fully Amortized Assets [Member]          
Impairment Of Long Lived Assets [Line Items]          
Impairment charges land held for sale     $ 1,900,000    
Amortization of intangibles     $ 1,900,000