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Significant Payors	12 Months Ended
Significant Payors	Dec. 31, 2011
Significant Payors [Abstract]
Significant Payors	14. Significant Payors A substantial portion of the Company's net service revenues and accounts receivables are derived from services performed for federal, state and local governmental agencies. Medicare and one state governmental agency represented 12% and 43%; 12% and 38%; and 12% and 34% of the Company's net service revenues for 2011, 2010, and 2009, respectively. The related receivables due from Medicare and the state agency represented 11% and 58% of the Company's accounts receivable at December 31, 2011, respectively, and 9% and 58% of the Company's accounts receivable at December 31, 2010, respectively.