Condensed Consolidated Statements of Changes in Equity and Income (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par	Retained Earnings (Accumulated Deficit)	Total Stockholders’ Equity	Non-controlling Interests
Balance (in shares) at Dec. 31, 2018		135,266,000
Balance at Dec. 31, 2018	$ 916,240	$ 135	$ 482,556	$ 320,351	$ 803,042	$ 113,198
Increase (Decrease) in Stockholders' Equity
Net income attributable to Select Medical Holdings Corporation	40,834			40,834	40,834
Net income attributable to non-controlling interests	4,810					4,810
Issuance of restricted stock (in shares)		21,000
Issuance of restricted stock	0	$ 0	0
Forfeitures of unvested restricted stock (in shares)		(24,000)
Forfeitures of unvested restricted stock	0	$ 0	0
Vesting of restricted stock	5,488		5,488		5,488
Issuance of non-controlling interests	6,837					6,837
Distributions to and purchases of non-controlling interests	(2,480)		259		259	(2,739)
Redemption adjustment on non-controlling interests	(47,470)			(47,470)	(47,470)
Other	291			(122)	(122)	413
Balance (in shares) at Mar. 31, 2019		135,263,000
Balance at Mar. 31, 2019	$ 924,550	$ 135	488,303	313,593	802,031	122,519
Balance (in shares) at Dec. 31, 2019	134,328,112	134,328,000
Balance at Dec. 31, 2019	$ 929,035	$ 134	491,038	279,800	770,972	158,063
Increase (Decrease) in Stockholders' Equity
Net income attributable to Select Medical Holdings Corporation	53,125			53,125	53,125
Net income attributable to non-controlling interests	10,067					10,067
Issuance of restricted stock (in shares)		2,000
Issuance of restricted stock	0	$ 0	0
Forfeitures of unvested restricted stock (in shares)		(15,000)
Forfeitures of unvested restricted stock	0	$ 0	0
Vesting of restricted stock	6,136		6,136		6,136
Repurchase of common shares (in shares)		(492,000)
Repurchase of common shares	(8,691)	$ 0	(5,350)	(3,341)	(8,691)
Issuance of non-controlling interests	1,679					1,679
Distributions to and purchases of non-controlling interests	(6,774)			(2,726)	(2,726)	(4,048)
Redemption adjustment on non-controlling interests	(10,123)			(10,123)	(10,123)
Other	$ 365			(55)	(55)	420
Balance (in shares) at Mar. 31, 2020	133,823,713	133,823,000
Balance at Mar. 31, 2020	$ 974,819	$ 134	$ 491,824	$ 316,680	$ 808,638	$ 166,181