Annual report pursuant to Section 13 and 15(d)

Operating Leases (Details)

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Operating Leases (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Operating Leases [Abstract]      
Operating lease renewal option, minimum (in years) 1 year    
Operating lease renewal option, maximum (in years) 10 years    
Operating lease original term, for tractors, trucks and trailers, minimum (in years) 3 years    
Operating lease original term, for tractors, trucks and trailers, maximum (in years) 6 years    
Sublease rental income $ 770 $ 556 $ 356
Expected future sublease rental income 95    
Operating Leases, Future Minimum Payments Due [Abstract]      
2012 19,682    
2013 16,673    
2014 14,882    
2015 11,422    
2016 7,104    
Thereafter 8,950    
Total $ 78,713