v2.4.0.6
Financial Instruments (Details Textual) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Commodity Hedges [Member]
     
Financial Instruments (Textual) [Abstract]      
Aggregated fair values of outstanding hedges, current assets $ 1.4 $ 1.9  
Aggregated fair values of outstanding hedges, current liabilities 0.7 6.5  
Effective portions of changes in fair values recorded in stockholders equity as components of accumulated other comprehensive income 0.4 (2.6)  
Purchased put option [Member]
     
Financial Instruments (Textual) [Abstract]      
Notional Amount (in Gallons per Month) 25,000    
Written call option [Member]
     
Financial Instruments (Textual) [Abstract]      
Notional Amount (in Gallons per Month) 25,000    
Fuel hedges [Member]
     
Financial Instruments (Textual) [Abstract]      
Aggregated fair values of outstanding hedges, current assets 1.6 1.6  
Aggregated fair values of outstanding hedges, current liabilities 4.7 1.9  
Effective portions of changes in fair values recorded in stockholders equity as components of accumulated other comprehensive income 1.8 0.2  
Realized (losses) gains fuel hedges included in cost of operations in consolidated statements of income $ 0.9 $ (2.0) $ (7.3)
Costless collar agreements [Member]
     
Financial Instruments (Textual) [Abstract]      
Forecasted maximum sales of costless collar agreement 25,000