Summary of Significant Accounting Policies (Details 1)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Percentage of net service revenue
Percentage of net service revenue	100.00%	100.00%	100.00%
Medicare [Member]
Percentage of net service revenue
Percentage of net service revenue	77.90%	79.70%	80.50%
Medicaid [Member]
Percentage of net service revenue
Percentage of net service revenue	1.80%	2.30%	2.70%
Other [Member]
Percentage of net service revenue
Percentage of net service revenue	20.30%	18.00%	16.80%