Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,534,221	$ 1,423,869	$ 4,644,704	$ 4,071,219
Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	1,425,155	1,305,282	4,336,197	3,748,809
Medicare
Disaggregation of Revenue [Line Items]
Total revenue	352,950	346,538	1,074,635	1,027,427
Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	1,072,205	958,744	3,261,562	2,721,382
Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	109,066	118,587	308,507	322,410
Operating Segments | Critical Illness Recovery Hospital
Disaggregation of Revenue [Line Items]
Total revenue	530,646	519,454	1,669,577	1,539,601
Operating Segments | Critical Illness Recovery Hospital | Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	526,194	514,485	1,661,613	1,528,514
Operating Segments | Critical Illness Recovery Hospital | Medicare
Disaggregation of Revenue [Line Items]
Total revenue	201,337	218,386	634,675	675,403
Operating Segments | Critical Illness Recovery Hospital | Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	324,857	296,099	1,026,938	853,111
Operating Segments | Critical Illness Recovery Hospital | Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	4,452	4,969	7,964	11,087
Operating Segments | Rehabilitation Hospital
Disaggregation of Revenue [Line Items]
Total revenue	212,434	188,075	632,904	538,761
Operating Segments | Rehabilitation Hospital | Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	201,838	178,189	601,863	509,584
Operating Segments | Rehabilitation Hospital | Medicare
Disaggregation of Revenue [Line Items]
Total revenue	105,512	90,650	311,752	252,912
Operating Segments | Rehabilitation Hospital | Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	96,326	87,539	290,111	256,672
Operating Segments | Rehabilitation Hospital | Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	10,596	9,886	31,041	29,177
Operating Segments | Outpatient Rehabilitation
Disaggregation of Revenue [Line Items]
Total revenue	274,540	240,042	806,910	662,429
Operating Segments | Outpatient Rehabilitation | Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	256,656	223,630	756,950	616,504
Operating Segments | Outpatient Rehabilitation | Medicare
Disaggregation of Revenue [Line Items]
Total revenue	45,779	37,216	127,361	98,097
Operating Segments | Outpatient Rehabilitation | Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	210,877	186,414	629,589	518,407
Operating Segments | Outpatient Rehabilitation | Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	17,884	16,412	49,960	45,925
Operating Segments | Concentra
Disaggregation of Revenue [Line Items]
Total revenue	442,190	391,859	1,321,402	1,102,732
Operating Segments | Concentra | Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	440,467	388,978	1,315,771	1,094,207
Operating Segments | Concentra | Medicare
Disaggregation of Revenue [Line Items]
Total revenue	322	286	847	1,015
Operating Segments | Concentra | Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	440,145	388,692	1,314,924	1,093,192
Operating Segments | Concentra | Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	1,723	2,881	5,631	8,525
Other
Disaggregation of Revenue [Line Items]
Total revenue	74,411	84,439	213,911	227,696
Other | Patient services revenue
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Other | Medicare
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Other | Non-Medicare
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Other | Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 74,411	$ 84,439	$ 213,911	$ 227,696