Significant Accounting Policies - Percentage of Net Service Revenue Earned by Type of Ownership or Relationship with Operating Entity (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	100.00%	100.00%	100.00%	100.00%
Wholly-owned subsidiaries
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	54.50%	49.30%	52.90%	48.40%
Equity joint ventures
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	42.90%	48.10%	44.50%	48.90%
License leasing arrangements
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	1.80%	1.80%	1.80%	1.90%
Management services
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.80%	0.80%	0.80%	0.80%