Long-Term Debt and Notes Payable - Principal Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 06, 2017	Dec. 31, 2016	May 28, 2013
Long-term debt and notes payable
2018	$ 22,186
2019	14,875
2020	37,987
2021	728,426
2022	851,332
Thereafter	1,089,274
Total	2,744,080		$ 2,747,856
Select Excluding Concentra
Long-term debt and notes payable
2018	19,586
2019	14,721
2020	34,799
2021	721,736
2022	241,510
Thereafter	1,085,900
Total	2,118,252		2,100,439
Concentra Inc
Long-term debt and notes payable
2018	2,600
2019	154
2020	3,188
2021	6,690
2022	609,822
Thereafter	3,374
Total	625,828		647,417
Senior notes | Select Excluding Concentra | 6.375% Senior Notes Due June 2021
Long-term debt and notes payable
2018	0
2019	0
2020	0
2021	710,000
2022	0
Thereafter	0
Total	$ 710,000		$ 710,000
Interest rate of debt (as a percent)	6.375%	6.375%	6.375%	6.375%
Credit facility | Revolving facility | Select Excluding Concentra
Long-term debt and notes payable
2018	$ 0
2019	0
2020	0
2021	0
2022	230,000
Thereafter	0
Total	230,000		$ 220,000
Credit facility | Term loan | Select Excluding Concentra
Long-term debt and notes payable
2018	11,500
2019	11,500
2020	11,500
2021	11,500
2022	11,500
Thereafter	1,083,875
Total	1,141,375		1,147,751
Credit facility | Term loan | Concentra Inc
Long-term debt and notes payable
2018	0
2019	0
2020	3,016
2021	6,520
2022	609,639
Thereafter	0
Total	619,175		642,239
Other | Select Excluding Concentra
Long-term debt and notes payable
2018	8,086
2019	3,221
2020	23,299
2021	236
2022	10
Thereafter	2,025
Total	36,877		22,688
Other | Concentra Inc
Long-term debt and notes payable
2018	2,600
2019	154
2020	172
2021	170
2022	183
Thereafter	3,374
Total	$ 6,653		$ 5,178