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Consolidated Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Condensed Balance Sheets [Abstract]
Allowance for bad debts	$ 1,724	$ 1,544
Accumulated depreciation and amortization on property, plant and equipment	$ 993,410	$ 970,276

- 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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