Annual report pursuant to Section 13 and 15(d)

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

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Impairment of Long-Lived Assets - Additional Information (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
Impairment Or Disposal Of Tangible Assets Disclosure [Abstract]  
Estimated aggregate remaining fair value of long-lived assets impaired during current period $ 8,953