Significant Accounting Policies (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Percentage of net service revenue
Percentage of net service revenue	100.00%	100.00%	100.00%	100.00%
Equity joint ventures [Member]
Percentage of net service revenue
Percentage of net service revenue	49.10%	47.60%	48.70%	46.90%
Wholly-owned subsidiaries [Member]
Percentage of net service revenue
Percentage of net service revenue	48.10%	49.00%	48.50%	49.80%
License leasing arrangements [Member]
Percentage of net service revenue
Percentage of net service revenue	1.90%	2.40%	1.90%	2.30%
Management services [Member]
Percentage of net service revenue
Percentage of net service revenue	0.90%	1.00%	0.90%	1.00%