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Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Concentration Risk [Line Items]
Allowance for Doubtful Accounts Receivable, Recoveries	$ 1,400,000
(Recovery of ) provision for loss on accounts receivable	(543,000)	915,000	(1,455,000)
Credit Concentration Risk [Member]
Concentration Risk [Line Items]
(Recovery of ) provision for loss on accounts receivable	$ 817,000	$ 2,343,000	$ 1,117,000
Customer 1 [Member] \| Sales [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk percentage	4.00%
Minimum [Member] \| Customer 2 [Member] \| Sales [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk percentage	3.00%
Canada [Member] \| Sales [Member]
Concentration Risk [Line Items]
Concentration risk percentage	9.00%	9.00%	10.00%
Canada [Member] \| Sales [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk percentage	9.00%

Amount of the current period expense charged against operations, the offset which is generally to the allowance for doubtful accounts for the purpose of reducing receivables, including notes receivable, to an amount that approximates their net realizable value (the amount expected to be collected).

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