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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
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	57.60%	54.50%	57.30%	54.50%
Equity joint ventures
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	40.70%	43.60%	41.00%	43.50%
License leasing arrangements
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.90%	1.00%	0.90%	1.10%
Management services
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.80%	0.90%	0.80%	0.90%