Long-Term Debt and Notes Payable - Principal Maturities Of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2018	$ 8,208
2019	20,516
2020	41,850
2021	734,432
2022	1,232,915
Thereafter	1,342,363
Total	3,380,284	$ 2,744,080
Select Excluding Concentra
Debt Instrument [Line Items]
2018	6,867
2019	16,891
2020	35,785
2021	721,721
2022	76,500
Thereafter	1,098,990
Total	$ 1,956,754	2,118,252
Select Excluding Concentra | Senior notes | 6.375% Senior Notes Due June 2021
Debt Instrument [Line Items]
Interest rate of debt (as a percent)	6.375%
2018	$ 0
2019	0
2020	0
2021	710,000
2022	0
Thereafter	0
Total	710,000	710,000
Select Excluding Concentra | Credit facilities | Revolving facility
Debt Instrument [Line Items]
2018	0
2019	0
2020	0
2021	0
2022	65,000
Thereafter	0
Total	65,000	230,000
Select Excluding Concentra | Credit facilities | Term loans
Debt Instrument [Line Items]
2018	2,875
2019	11,500
2020	11,500
2021	11,500
2022	11,500
Thereafter	1,083,875
Total	1,132,750	1,141,375
Select Excluding Concentra | Other
Debt Instrument [Line Items]
2018	3,992
2019	5,391
2020	24,285
2021	221
2022	0
Thereafter	15,115
Total	49,004	36,877
Concentra Inc
Debt Instrument [Line Items]
2018	1,341
2019	3,625
2020	6,065
2021	12,711
2022	1,156,415
Thereafter	243,373
Total	1,423,530	625,828
Concentra Inc | Credit facilities | Term loans
Debt Instrument [Line Items]
2018	0
2019	0
2020	5,719
2021	12,365
2022	1,156,091
Thereafter	240,000
Total	1,414,175	619,175
Concentra Inc | Other
Debt Instrument [Line Items]
2018	1,341
2019	3,625
2020	346
2021	346
2022	324
Thereafter	3,373
Total	$ 9,355	$ 6,653