Segment Information - Selected Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenue	$ 1,599,547	$ 1,546,463
Adjusted EBITDA	163,847	258,341
Total assets	7,535,944	7,920,781	$ 7,360,171
Purchases of property and equipment	46,845	39,719
Government assistance recognized in earnings, CARES Act		16,100
Operating Segments | Critical Illness Recovery Hospital
Segment Reporting Information [Line Items]
Revenue	601,755	594,872
Adjusted EBITDA	35,967	113,272
Total assets	2,367,490	2,233,067
Purchases of property and equipment	19,569	14,385
Operating Segments | Rehabilitation Hospital
Segment Reporting Information [Line Items]
Revenue	220,634	207,804
Adjusted EBITDA	42,379	50,534
Total assets	1,187,118	1,188,387
Purchases of property and equipment	6,274	665
Operating Segments | Outpatient Rehabilitation
Segment Reporting Information [Line Items]
Revenue	271,940	251,961
Adjusted EBITDA	26,596	26,329
Total assets	1,350,374	1,321,268
Purchases of property and equipment	9,414	7,335
Operating Segments | Concentra
Segment Reporting Information [Line Items]
Revenue	423,423	422,840
Adjusted EBITDA	89,469	82,015
Total assets	2,339,940	2,468,157
Purchases of property and equipment	10,240	12,680
Other
Segment Reporting Information [Line Items]
Revenue	81,795	68,986
Adjusted EBITDA	(30,564)	(13,809)
Total assets	291,022	709,902
Purchases of property and equipment	$ 1,348	$ 4,654