Segment Information - Reconciliation of Adjusted EBITDA to Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment information
Adjusted EBITDA	$ 178,228	$ 158,680	$ 341,460	$ 297,570
Depreciation and amortization	(51,724)	(38,333)	(98,495)	(80,872)
Income (loss) from operations	120,561	115,663	229,159	207,428
Loss on early retirement of debt			(10,255)	(19,719)
Equity in earnings of unconsolidated subsidiaries	4,785	5,666	9,482	11,187
Non-operating gain (loss)	6,478	0	6,877	(49)
Interest expense	(50,159)	(37,655)	(97,322)	(78,508)
Income before income taxes	81,665	83,674	137,941	120,339
Operating Segments | Critical Illness Recovery Hospital
Segment information
Adjusted EBITDA	60,725	75,043	133,697	147,380
Depreciation and amortization	(11,952)	(10,917)	(23,010)	(23,959)
Stock compensation expense	0	0	0	0
U.S. HealthWorks acquisition costs	0		0
Income (loss) from operations	48,773	64,126	110,687	123,421
Operating Segments | Rehabilitation Hospital
Segment information
Adjusted EBITDA	28,195	23,129	54,971	39,457
Depreciation and amortization	(6,015)	(4,537)	(11,737)	(9,995)
Stock compensation expense	0	0	0	0
U.S. HealthWorks acquisition costs	0		0
Income (loss) from operations	22,180	18,592	43,234	29,462
Operating Segments | Outpatient Rehabilitation
Segment information
Adjusted EBITDA	41,947	41,926	72,472	73,277
Depreciation and amortization	(6,704)	(5,878)	(13,341)	(12,218)
Stock compensation expense	0	0	0	0
U.S. HealthWorks acquisition costs	0		0
Income (loss) from operations	35,243	36,048	59,131	61,059
Operating Segments | Concentra
Segment information
Adjusted EBITDA	72,568	43,061	130,365	85,653
Depreciation and amortization	(24,697)	(15,429)	(45,844)	(31,552)
Stock compensation expense	(1,138)	(264)	(1,349)	(570)
U.S. HealthWorks acquisition costs	41		(2,895)
Income (loss) from operations	46,774	27,368	80,277	53,531
Other
Segment information
Adjusted EBITDA	(25,207)	(24,479)	(50,045)	(48,197)
Depreciation and amortization	(2,356)	(1,572)	(4,563)	(3,148)
Stock compensation expense	(4,846)	(4,420)	(9,562)	(8,700)
U.S. HealthWorks acquisition costs	0		0
Income (loss) from operations	$ (32,409)	$ (30,471)	$ (64,170)	$ (60,045)