Segment Information - Reconciliation of Adjusted EBITDA to Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment information
Adjusted EBITDA	$ 163,232	$ 138,890
Depreciation and amortization	(46,771)	(42,539)
Income (loss) from operations	108,598	91,765
Loss on early retirement of debt	(10,255)	(19,719)
Equity in earnings of unconsolidated subsidiaries	4,697	5,521
Non-operating gain (loss)	399	(49)
Interest expense	(47,163)	(40,853)
Income (loss) before income taxes	56,276	36,665
Operating Segments | Long Term Acute Care
Segment information
Adjusted EBITDA	72,972	72,337
Depreciation and amortization	(11,058)	(13,042)
Stock compensation expense	0	0
U.S. HealthWorks acquisition costs	0
Income (loss) from operations	61,914	59,295
Operating Segments | Inpatient Rehabilitation
Segment information
Adjusted EBITDA	26,776	16,328
Depreciation and amortization	(5,722)	(5,458)
Stock compensation expense	0	0
U.S. HealthWorks acquisition costs	0
Income (loss) from operations	21,054	10,870
Operating Segments | Outpatient Rehabilitation
Segment information
Adjusted EBITDA	30,525	31,351
Depreciation and amortization	(6,637)	(6,340)
Stock compensation expense	0	0
U.S. HealthWorks acquisition costs	0
Income (loss) from operations	23,888	25,011
Operating Segments | Concentra
Segment information
Adjusted EBITDA	57,797	42,592
Depreciation and amortization	(21,147)	(16,123)
Stock compensation expense	(211)	(306)
U.S. HealthWorks acquisition costs	(2,936)
Income (loss) from operations	33,503	26,163
Other
Segment information
Adjusted EBITDA	(24,838)	(23,718)
Depreciation and amortization	(2,207)	(1,576)
Stock compensation expense	(4,716)	(4,280)
U.S. HealthWorks acquisition costs	0
Income (loss) from operations	$ (31,761)	$ (29,574)