Summary of Significant Accounting Policies - Estimated Useful Lives of Assets (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2012
Vehicles and others [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life		5 years
Minimum [Member] | Buildings [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life		30 years
Minimum [Member] | Building related structures [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life		10 years
Minimum [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life	5 years	10 years
Maximum [Member] | Buildings [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life		40 years
Maximum [Member] | Building related structures [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life		20 years
Maximum [Member] | Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, estimated useful life	10 years	12 years