Segment Information - Reconciliation of Adjusted EBITDA to Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment information
Adjusted EBITDA	$ 187,333	$ 170,117
Depreciation and amortization	(51,752)	(52,138)
Income from operations	128,678	111,724
Equity in earnings of unconsolidated subsidiaries	2,588	4,366
Gain on sale of businesses	7,201	6,532
Interest expense	(46,107)	(50,811)
Income (loss) before income taxes	92,360	71,811
Operating Segments | Critical Illness Recovery Hospital
Segment information
Adjusted EBITDA	88,570	72,998
Depreciation and amortization	(12,336)	(11,451)
Stock compensation expense	0	0
Income from operations	76,234	61,547
Operating Segments | Rehabilitation Hospital
Segment information
Adjusted EBITDA	38,569	25,797
Depreciation and amortization	(6,887)	(6,402)
Stock compensation expense	0	0
Income from operations	31,682	19,395
Operating Segments | Outpatient Rehabilitation
Segment information
Adjusted EBITDA	27,122	28,991
Depreciation and amortization	(7,218)	(7,032)
Stock compensation expense	0	0
Income from operations	19,904	21,959
Operating Segments | Concentra
Segment information
Adjusted EBITDA	61,466	66,258
Depreciation and amortization	(22,887)	(24,904)
Stock compensation expense	(767)	(767)
Income from operations	37,812	40,587
Other
Segment information
Adjusted EBITDA	(28,394)	(23,927)
Depreciation and amortization	(2,424)	(2,349)
Stock compensation expense	(6,136)	(5,488)
Income from operations	$ (36,954)	$ (31,764)