Cover - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-34465
Entity Registrant Name	SELECT MEDICAL HOLDINGS CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-1764048
Entity Address, Address Line One	4714 Gettysburg Road
Entity Address, Address Line Two	P.O. Box 2034
Entity Address, City or Town	Mechanicsburg
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	17055
City Area Code	717
Local Phone Number	972-1100
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	SEM
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		133,977,064
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001320414