Summary of Significant Accounting Policies - Percentage of Net Service Revenue Earned by Type of Ownership or Relationship with Operating Entity (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	100.00%	100.00%	100.00%
Wholly-owned Subsidiaries [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	48.80%	48.10%	49.50%
Equity Joint Ventures [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	48.50%	49.10%	47.10%
License Leasing Arrangements [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	1.90%	1.90%	2.40%
Management Services [Member]
Health Care Organization, Revenue [Abstract]
Percentage of net service revenue	0.80%	0.90%	1.00%