Significant Accounting Policies - Percentage of Net Service Revenue Earned by Type of Ownership or Relationship with Operating Entity (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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	57.00%	54.50%	56.90%	54.20%
Equity joint ventures
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	41.30%	43.60%	41.40%	43.70%
License leasing arrangements
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.90%	1.00%	0.90%	1.20%
Management services
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.80%	0.90%	0.80%	0.90%