Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 1,882,744	$ 1,857,618
Less accumulated depreciation	(664,519)	(600,648)
Property plant and equipment, net	1,218,225	1,256,970
Depreciation expense	62,194	63,550	63,855
Undivided interest in property plant and equipment comprising Mt. Holly inclusive of gross property, plant and equipment	176,029	173,532
Undivided interest in property, plant and equipment comprising Mt. Holly inclusive of accumulated depreciation	105,585	98,279
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	13,021	13,040
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	320,552	318,767
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	1,387,010	1,381,524
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 162,161	$ 144,287

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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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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- Definition

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.

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- Definition

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.

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