Significant Accounting Policies - Percentage of Net Service Revenue Earned by Type of Ownership or Relationship with Operating Entity (Detail)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	100.00%	100.00%
Wholly-owned subsidiaries [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	49.20%	47.20%
Equity joint ventures [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	48.00%	50.10%
License leasing arrangements [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	1.90%	1.80%
Management services [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.90%	0.90%