Quarterly report pursuant to Section 13 or 15(d)

Consolidated Condensed Balance Sheets (Parenthetical)

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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