Long-Term Debt and Notes Payable - Components of Long-Term Debt And Notes Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Long-term debt and notes payable
Principal Outstanding	$ 3,464,081	$ 2,744,080
Unamortized Premium (Discount)	(14,068)	(13,924)
Unamortized Issuance Costs	(39,325)	(30,254)
Carrying Value	3,410,688	2,699,902
Fair Value	3,473,116	2,761,735
Select Excluding Concentra
Long-term debt and notes payable
Principal Outstanding	2,039,305	2,118,252
Unamortized Premium (Discount)	(10,780)	(11,667)
Unamortized Issuance Costs	(17,605)	(19,586)
Carrying Value	2,010,920	2,086,999
Fair Value	$ 2,047,675	2,129,909
Select Excluding Concentra \| Senior notes \| 6.375% Senior Notes Due June 2021
Long-term debt and notes payable
Interest rate of debt (as a percent)	6.375%
Principal Outstanding	$ 710,000	710,000
Unamortized Premium (Discount)	664	778
Unamortized Issuance Costs	(5,601)	(6,553)
Carrying Value	705,063	704,225
Fair Value	718,094	727,750
Select Excluding Concentra \| Other
Long-term debt and notes payable
Principal Outstanding	43,680	36,877
Unamortized Premium (Discount)	0	0
Unamortized Issuance Costs	(500)	(533)
Carrying Value	43,180	36,344
Fair Value	43,180	36,344
Select Excluding Concentra \| Revolving facility \| Credit facility
Long-term debt and notes payable
Principal Outstanding	150,000	230,000
Unamortized Premium (Discount)	0	0
Unamortized Issuance Costs	0	0
Carrying Value	150,000	230,000
Fair Value	138,000	211,600
Select Excluding Concentra \| Term loan \| Credit facility
Long-term debt and notes payable
Principal Outstanding	1,135,625	1,141,375
Unamortized Premium (Discount)	(11,444)	(12,445)
Unamortized Issuance Costs	(11,504)	(12,500)
Carrying Value	1,112,677	1,116,430
Fair Value	1,148,401	1,154,215
Concentra Inc
Long-term debt and notes payable
Principal Outstanding	1,424,776	625,828
Unamortized Premium (Discount)	(3,288)	(2,257)
Unamortized Issuance Costs	(21,720)	(10,668)
Carrying Value	1,399,768	612,903
Fair Value	1,425,441	631,826
Concentra Inc \| Other
Long-term debt and notes payable
Principal Outstanding	10,601	6,653
Unamortized Premium (Discount)	0	0
Unamortized Issuance Costs	0	0
Carrying Value	10,601	6,653
Fair Value	10,601	6,653
Concentra Inc \| Term loan \| Credit facility
Long-term debt and notes payable
Principal Outstanding	1,414,175	619,175
Unamortized Premium (Discount)	(3,288)	(2,257)
Unamortized Issuance Costs	(21,720)	(10,668)
Carrying Value	1,389,167	606,250
Fair Value	$ 1,414,840	$ 625,173

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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