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, 2015
Dec. 31, 2014
Statement of Financial Position [Abstract]    
Allowance for bad debts $ 9,289us-gaap_AllowanceForNotesAndLoansReceivableCurrent $ 11,188us-gaap_AllowanceForNotesAndLoansReceivableCurrent
Accumulated depreciation and amortization on property, plant and equipment $ 1,223,119us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment $ 1,201,058us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment