Business Segments - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 589,613	$ 471,308
Percentage of revenue	100.00%	100.00%
Medicaid
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 224,107	$ 184,499
Percentage of revenue	38.00%	39.10%
Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 155,584	$ 116,701
Percentage of revenue	26.40%	24.80%
Medicaid — skilled
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 36,077	$ 30,451
Percentage of revenue	6.10%	6.50%
Total Medicaid and Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 415,768	$ 331,651
Percentage of revenue	70.50%	70.40%
Managed care
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 102,029	$ 83,172
Percentage of revenue	17.30%	17.60%
Private and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 71,816	$ 56,485
Percentage of revenue	12.20%	12.00%
Operating Segments | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 558,405	$ 449,258
Operating Segments | Medicaid | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	220,881	181,294
Operating Segments | Medicare | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	155,584	116,701
Operating Segments | Medicaid — skilled | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	36,077	30,451
Operating Segments | Total Medicaid and Medicare | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	412,542	328,446
Operating Segments | Managed care | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	102,029	83,172
Operating Segments | Private and other | Transitional and Skilled Services
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	43,834	37,640
All Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	31,208	22,050
All Other | Medicaid
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	3,226	3,205
All Other | Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0
All Other | Medicaid — skilled
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0
All Other | Total Medicaid and Medicare
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	3,226	3,205
All Other | Managed care
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	0	0
All Other | Private and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 27,982	$ 18,845