Segment Information - Selected Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment information
Net revenue	$ 1,114,401	$ 1,097,166	$ 1,120,675	$ 1,111,361	$ 1,046,265	$ 1,053,795	$ 1,097,631	$ 1,088,330	$ 4,443,603	$ 4,286,021	$ 3,742,736
Adjusted EBITDA									537,992	465,807	399,165
Total assets	(5,127,166)				(4,920,626)				(5,127,166)	(4,920,626)	(4,388,678)
Capital expenditures									233,243	161,633	182,642
Accounting Standards Update 2015-17 | Restatement Adjustment
Segment information
Total assets					23,800					23,800
Other
Segment information
Net revenue									700	541	724
Adjusted EBITDA									(94,822)	(88,543)	(74,979)
Total assets	(114,286)				(107,318)				(114,286)	(107,318)	(103,692)
Capital expenditures									30,413	15,262	12,089
Long Term Acute Care
Segment information
Real estate assets held for sale	9,800				24,400				9,800	24,400	2,700
Long Term Acute Care | Operating Segments
Segment information
Net revenue									1,756,243	1,785,164	1,902,776
Adjusted EBITDA									252,679	224,609	258,223
Total assets	(1,848,783)				(1,910,013)				(1,848,783)	(1,910,013)	(1,954,823)
Capital expenditures									49,720	48,626	39,784
Inpatient Rehabilitation | Operating Segments
Segment information
Net revenue									631,777	504,318	444,005
Adjusted EBITDA									90,041	56,902	69,400
Total assets	(868,517)				(621,105)				(868,517)	(621,105)	(470,290)
Capital expenditures									96,477	60,513	86,230
Outpatient Rehabilitation | Operating Segments
Segment information
Net revenue									1,020,848	995,374	810,009
Adjusted EBITDA									132,533	129,830	98,220
Total assets	(954,661)				(969,014)				(954,661)	(969,014)	(548,242)
Capital expenditures									27,721	21,286	17,768
Concentra | Operating Segments
Segment information
Net revenue									1,034,035	1,000,624	585,222
Adjusted EBITDA									157,561	143,009	48,301
Total assets	$ (1,340,919)				$ (1,313,176)				(1,340,919)	(1,313,176)	(1,311,631)
Capital expenditures									$ 28,912	$ 15,946	$ 26,771