Impairment of Long-Lived Assets - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016
Impairment Or Disposal Of Tangible Assets Disclosure [Abstract]
Estimated aggregate fair value of long-lived assets impaired during current period	$ 5,367
Multiple of cash flows used to estimate fair value of long-lived asset	6.5	6.5