Business Segments - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 599,255	$ 512,109	$ 1,773,567	$ 1,476,333
Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	100.00%	100.00%	100.00%	100.00%
Medicaid
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 222,192	$ 205,945	$ 672,506	$ 586,222
Medicaid | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	37.10%	40.20%	37.90%	39.70%
Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 189,237	$ 119,633	$ 519,865	$ 355,141
Medicare | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	31.60%	23.40%	29.30%	24.10%
Medicaid — skilled
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 38,232	$ 34,080	$ 110,626	$ 96,323
Medicaid — skilled | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	6.40%	6.60%	6.30%	6.50%
Total Medicaid and Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 449,661	$ 359,658	$ 1,302,997	$ 1,037,686
Total Medicaid and Medicare | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	75.10%	70.20%	73.50%	70.30%
Managed care
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 87,648	$ 88,542	$ 271,993	$ 258,205
Managed care | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	14.60%	17.30%	15.30%	17.50%
Private and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 61,946	$ 63,909	$ 198,577	$ 180,442
Private and other | Revenue Benchmark | Customer Concentration Risk
Segment Reporting, Revenue Reconciling Item [Line Items]
Concentration risk	10.30%	12.50%	11.20%	12.20%
Operating Segments | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 570,384	$ 485,973	$ 1,685,568	$ 1,404,469
Operating Segments | Medicaid | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	218,840	202,665	662,733	576,504
Operating Segments | Medicare | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	189,237	119,633	519,865	355,141
Operating Segments | Medicaid — skilled | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	38,232	34,080	110,626	96,323
Operating Segments | Total Medicaid and Medicare | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	446,309	356,378	1,293,224	1,027,968
Operating Segments | Managed care | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	87,648	88,542	271,993	258,205
Operating Segments | Private and other | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	36,427	41,053	120,351	118,296
All Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	28,871	26,136	87,999	71,864
All Other | Medicaid
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	3,352	3,280	9,773	9,718
All Other | Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0	0	0
All Other | Medicaid — skilled
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0	0	0
All Other | Total Medicaid and Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	3,352	3,280	9,773	9,718
All Other | Managed care
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0	0	0
All Other | Private and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 25,519	$ 22,856	$ 78,226	$ 62,146