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CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 11,640	$ 11,113
Land and depreciable assets, accumulated depreciation (in dollars)	$ 673,265	$ 655,869

- Definition

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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