Property, Plant and Equipment, at Cost (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012
Minimum | Short-Lived Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Minimum | Production Process Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	8 years
Minimum | Production Process Equipment (Major Unit Components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	20 years
Minimum | Production Process Equipment (Infrastructure and Other)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	30 years
Maximum | Short-Lived Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Maximum | Production Process Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	19 years
Maximum | Production Process Equipment (Major Unit Components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	29 years
Maximum | Production Process Equipment (Infrastructure and Other)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	45 years