Supplemental Financial Information of Concentra Group Holdings Parent - Schedule of Condensed Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Income Statements, Captions [Line Items]
Net operating revenues	$ 1,393,343			$ 1,267,401			$ 4,079,338	$ 3,816,575
Income from operations	122,906			99,837			359,512	328,996
Net income	44,030			42,679			157,360	147,220
Net income attributable to Select Medical Holdings Corporation	30,732	$ 44,816	$ 40,834	32,917	$ 46,511	$ 33,739	116,382	113,167
Concentra Group Holdings Parent, LLC
Condensed Income Statements, Captions [Line Items]
Net operating revenues	421,900			404,481			1,231,672	1,173,420
Income from operations	52,922			43,499			144,350	123,776
Net income	17,788			16,084			53,521	45,576
Net income attributable to Select Medical Holdings Corporation	$ 8,124			$ 7,486			$ 24,534	$ 20,778