Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies (Narrative) (Details)

v2.4.0.6
Significant Accounting Policies (Narrative) (Details) (USD $)
0 Months Ended 12 Months Ended
Aug. 23, 2010
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Significant Accounting Policies [Line Items]        
Common stock split description those shareholders received one additional share of common stock for every two shares owned.      
Depreciation expenses including capital leases   $ 89,900,000 $ 79,400,000 $ 93,900,000
Increase in income from continuing operations     12,700,000  
Increase in net income     7,700,000  
Other intangible assets   8,100,000 8,100,000  
Accumulated amortization of intangible assets   4,700,000 3,800,000  
Amortization expense   900,000 900,000 900,000
Self insurance additional coverage   200,000    
Maximum self-insured long-term disability claims for employees per month   3,000    
Last payment date of self-insured long-term disability claims for salaried employees   April 2, 2010    
Last payment date of self-insured long-term disability claims for non-salaried employees   July 1, 2011    
Self-insurance reserve   86,000,000 79,300,000  
Long-term portions of self insurance reserve   50,100,000 45,400,000  
Advertising expense   8,300,000 6,300,000 4,100,000
Company-owned life insurance contracts   27,600,000 25,800,000  
Senior notes, fair value   270,300,000 212,300,000  
Trailers [Member]
       
Significant Accounting Policies [Line Items]        
Estimated average useful lives of asset, years   15    
Estimated previous useful lives of asset, years   12    
Tractors [Member]
       
Significant Accounting Policies [Line Items]        
Estimated average useful lives of asset, years   9    
Estimated previous useful lives of asset, years   7    
Group Health Claims [Member]
       
Significant Accounting Policies [Line Items]        
Insurance maximum, per occurrence   375,000    
Workers Compensation Claims [Member]
       
Significant Accounting Policies [Line Items]        
Insurance maximum, per occurrence   1,000,000    
Cargo Loss And Damage Claims [Member]
       
Significant Accounting Policies [Line Items]        
Insurance maximum, per occurrence   100,000    
Bodily Injury And Property Damage [Member]
       
Significant Accounting Policies [Line Items]        
Insurance maximum, per occurrence   $ 2,750,000