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Income Taxes (Details) (USD $)	3 Months Ended
Income Taxes (Details) (USD $)	Mar. 31, 2012	Mar. 31, 2011
INCOME TAXES [Abstract]
Effective income tax rate, continuing operations	35.60%	27.70%
Tax credits percentage of qualified maintenance expenditures to reduce federal income tax	50.00%
Tax credits limitation per mile on maintenance expenditures to reduce federal income tax	$ 3,500

- Definition

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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