Property Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Property, plant and equipment
Land	$ 14,677	$ 14,258
Buildings and improvements	134,628	131,164
Machinery and equipment	219,993	192,747
Mats (rental fleet)	40,597	37,964
Construction in progress	3,520	4,535
Property, plant and equipment Gross	413,415	380,668
Less accumulated depreciation	(182,360)	(168,013)
Property, plant and equipment, net	$ 231,055	$ 212,655

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, as of the balance sheet date, of long-lived, depreciable assets that include building structures held for productive use including any addition, improvement, or renovation to the structure, such as interior masonry, interior flooring, electrical, and plumbing.

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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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