Property, Plant, Equipment and Development (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Property, plant and equipment
Property, plant and equipment, gross	$ 2,817.8	$ 2,718.5
Less: Accumulated depreciation, depletion and amortization	(195.2)	(179.6)
Property, plant and equipment, net	2,622.6	2,538.9
Mining properties and mineral reserves
Property, plant and equipment
Property, plant and equipment, gross	982.8	978.0
Mining and milling equipment and facilities
Property, plant and equipment
Property, plant and equipment, gross	493.7	467.5
Processing facilities
Property, plant and equipment
Property, plant and equipment, gross	165.9	165.8
Construction-in-progress
Property, plant and equipment
Property, plant and equipment, gross	1,156.7	1,089.0
Construction-in-progress \| Endako Mine joint venture
Property, plant and equipment
Property, plant and equipment, gross	1,147.9
Valuation allowances and reserves, balance	58.0	55.4
Construction-in-progress \| Mt. Milligan
Property, plant and equipment
Property, plant and equipment, gross		1,079.8
Other
Property, plant and equipment
Property, plant and equipment, gross	$ 18.7	$ 18.2

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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