Receivables Narrative (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	$ 22,122,000	$ 22,213,000
Number of Missed Payments before Delinquent	3	3
Typical Financing Period	12 months
Credit amount requiring additional analysis	250,000
Average Period of Adjudication	18 months
Installment receivable purchased from DLL	$ 1,035,000