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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
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%	54.50%	54.50%	52.90%
Equity joint ventures
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	43.60%	42.90%	43.50%	44.50%
License leasing arrangements
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	1.00%	1.80%	1.10%	1.80%
Management services
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.90%	0.80%	0.90%	0.80%