Property and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	$ 162,943,000	$ 146,910,000
Accumulated depreciation of property and equipment held under capital leases	96,895,000	86,999,000
Recorded depreciation expense	15,900,000	15,500,000	15,800,000
Medical and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Medical and other equipment held under capital leases	2,400,000	1,400,000
Accumulated depreciation of property and equipment held under capital leases	$ 1,400,000	$ 1,200,000