Property, Plant and Equipment (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	$ 10,475,149	$ 10,367,847
Property, plant and equipment, Cost	17,336,643	16,408,843
Mining Properties and Mineral Rights
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	619,950	432,051
Property, plant and equipment, Cost	1,078,770	779,036
Administrative assets and support equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	$ 21,154	$ 17,067

Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References+ Details

Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References+ Details