Property Plant and Equipment Net (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Land and land improvements	$ 645,095	$ 620,940
Mineral reserves and interests	430,884	421,820
Buildings	116,332	111,796
Machinery and equipment	2,511,222	2,407,045
Construction in progress	109,054	127,091
Gross property, plant and equipment	3,812,587	3,688,692
Less allowances for depreciation, depletion and amortization	(2,059,346)	(1,914,401)
Net property, plant and equipment	$ 1,753,241	$ 1,774,291

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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