Revenue Payor Mix (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Medicare and Medicaid
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	24.00%	29.00%
Commercial health insurance payors
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	67.00%	59.00%
Patient self-pay
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	4.00%	5.00%
Management fees from affiliates
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	5.00%	7.00%
Other
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	5.00%	4.00%
Provision for doubtful accounts
Health Care Organization Receivable And Revenue Disclosures [Line Items]
Revenues by payer type sales revenue percentage	(5.00%)	(4.00%)