Condensed Consolidated Statements of Changes in Equity and Income (unaudited) - USD ($) $ in Thousands	Total	Total Stockholders’ Equity	Common Stock	Capital in Excess of Par	Retained Earnings	Accumulated Other Comprehensive Income	Non-controlling Interests
Beginning balance (in shares) at Dec. 31, 2020			134,850,000
Beginning balance at Dec. 31, 2020	$ 1,252,973	$ 1,060,480	$ 135	$ 509,128	$ 553,244	$ (2,027)	$ 192,493
Increase (Decrease) in Stockholders' Equity
Net income attributable to Select Medical Holdings Corporation	110,546	110,546			110,546
Net income attributable to non-controlling interests	17,042	0					17,042
Issuance of restricted stock (in shares)			2,000
Issuance of restricted stock	0	0	$ 0	0
Forfeitures of unvested restricted stock (in shares)			(14,000)
Forfeitures of unvested restricted stock	0	0	$ 0	0
Vesting of restricted stock	6,173	6,173		6,173
Non-controlling interests acquired in business combination	8,193	0					8,193
Distributions to and purchases of non-controlling interests	(14,245)	(787)		(787)			(13,458)
Redemption value adjustment on non-controlling interests	(38,405)	(38,405)			(38,405)
Other comprehensive income	8,151	8,151				8,151
Other	189	(182)		(178)	(4)		371
Ending balance (in shares) at Mar. 31, 2021			134,838,000
Ending balance at Mar. 31, 2021	$ 1,350,617	1,145,976	$ 135	514,336	625,381	6,124	204,641
Beginning balance (in shares) at Dec. 31, 2021	133,884,817		133,884,000
Beginning balance at Dec. 31, 2021	$ 1,325,902	1,109,981	$ 134	504,314	593,251	12,282	215,921
Increase (Decrease) in Stockholders' Equity
Net income attributable to Select Medical Holdings Corporation	49,117	49,117			49,117
Net income attributable to non-controlling interests	4,891	0					4,891
Cash dividends declared for common stockholders ($0.125 per share)	(16,691)	(16,691)			(16,691)
Issuance of restricted stock (in shares)			13,000
Issuance of restricted stock	0	0	$ 0	0
Vesting of restricted stock	8,288	8,288		8,288
Repurchase of common shares (in shares)			(2,128,000)
Repurchase of common shares	(51,676)	(51,676)	$ (2)	(23,459)	(28,215)
Issuance of non-controlling interests	5,229	651		651			4,578
Non-controlling interests acquired in business combination	12,463	0					12,463
Distributions to and purchases of non-controlling interests	(9,097)	0					(9,097)
Redemption value adjustment on non-controlling interests	(1,381)	(1,381)			(1,381)
Other comprehensive income	39,853	39,853				39,853
Other	$ (2)	(2)			(2)
Ending balance (in shares) at Mar. 31, 2022	131,769,303		131,769,000
Ending balance at Mar. 31, 2022	$ 1,366,896	$ 1,138,140	$ 132	$ 489,794	$ 596,079	$ 52,135	$ 228,756