Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Related Assets (Detail)	12 Months Ended
	Dec. 31, 2017
Minimum [Member] | Machinery, equipment, vehicles and office furniture [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	2 years
Minimum [Member] | Building and building improvements [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	15 years
Minimum [Member] | Computer equipment and software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	3 years
Maximum [Member] | Machinery, equipment, vehicles and office furniture [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	12 years
Maximum [Member] | Building and building improvements [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	30 years
Maximum [Member] | Computer equipment and software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets (in years)	10 years