Estimated Useful Lives Used in Connection With Preparation of Financial Statements (Detail)	9 Months Ended
	Sep. 30, 2018
Buildings
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	30 years
Plant and machinery
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Motor vehicles
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Office furniture and electronic equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Office furniture and electronic equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years