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Accounts Receivable - Additional Information (Details) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2010
Customer in Bankruptcy
Dec. 31, 2008
Customer in Bankruptcy
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Allowance for doubtful accounts recoveries       $ 700,000  
Allowance for doubtful accounts write - offs 6,000 [1] 108,000 [1] 2,216,000 [1] 800,000  
Allowance for doubtful accounts reduction total       1,500,000  
Additions charged to costs and expenses $ 1,735,000 $ 2,511,000 $ 129,000   $ 1,500,000
[1] Deductions represent write-off of receivables and collections of amounts for which an allowance had previously been established.