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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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%	54.20%	52.00%
Equity joint ventures
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	43.60%	42.90%	43.70%	45.30%
License leasing arrangements
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	1.00%	1.80%	1.20%	1.90%
Management services
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.90%	0.80%	0.90%	0.80%