Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2013
Allowance for Doubtful Accounts

The following table summarizes activity in the allowance for doubtful accounts:

 

     2013     2012     2011  

Beginning balance at January 1,

    $ 6,128      $ 2,636      $ 1,232   

Bad debt expense

      3,275        6,517        2,206   

Write-offs, net

      (3,875 )      (3,025 )      (802 ) 
  

 

 

    

 

 

    

 

 

  

Ending balance at December 31,

    $ 5,528      $ 6,128      $ 2,636   
  

 

 

    

 

 

    

 

 

  
Depreciation Computed Using Estimated Useful Lives

The range of useful lives for the components of property, plant and equipment are as follows:

 

Buildings

      15-39 years   

Building improvements

      5-20 years   

Pipelines

      10-30 years   

Disposal wells

      3-10 years   

Machinery and equipment

      3-15 years   

Equipment under capital leases

      4-6 years   

Motor vehicles and trailers

      3-11 years   

Rental equipment

      5-15 years   

Office equipment

      3-7 years