Condensed Consolidating Financial Information - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net income	$ 42,679	$ 24,824	$ 147,220	$ 99,587
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			10,734	14,542
Depreciation and amortization	50,527	38,772	149,022	119,644
Provision for bad debts		169	(373)	914
Equity in earnings of unconsolidated subsidiaries	(5,432)	(4,431)	(14,914)	(15,618)
Loss on extinguishment of debt			484	6,527
Loss (gain) on sale of assets and businesses			(9,129)	(9,499)
Stock compensation expense			17,175	14,227
Amortization of debt discount, premium and issuance costs			9,845	8,546
Deferred income taxes			(2,092)	(6,126)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			23,495	(143,308)
Other current assets			(10,274)	(2,677)
Other assets			4,828	1,407
Accounts payable			(3,507)	3,913
Accrued expenses			49,391	18,752
Income taxes			9,072	19,141
Net cash provided by (used in) operating activities			380,977	129,972
Investing activities
Business combinations, net of cash acquired			(519,258)	(19,371)
Purchases of property and equipment	(39,391)	(68,498)	(121,039)	(173,800)
Investment in businesses			(12,936)	(11,374)
Proceeds from sale of assets and businesses			6,691	34,555
Net cash used in investing activities			(646,542)	(169,990)
Financing activities
Borrowings on revolving facilities			420,000	805,000
Payments on revolving facilities			(585,000)	(705,000)
Proceeds from term loans (financing costs)			779,904	1,139,487
Payments on term loans			(8,625)	(1,176,567)
Revolving facility debt issuance costs			(1,333)	(4,392)
Borrowings of other debt			30,134	27,571
Principal payments on other debt			(17,971)	(15,112)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Decrease in overdrafts			(6,172)	(20,439)
Proceeds from issuance of non-controlling interests			2,926	8,986
Distributions to non-controlling interests			(306,427)	(9,276)
Net cash provided by (used in) financing activities			303,429	48,289
Net increase (decrease) in cash and cash equivalents			37,864	8,271
Cash and cash equivalents at beginning of period			122,549	99,029
Cash and cash equivalents at end of period	160,413	107,300	160,413	107,300
Consolidating and Eliminating Adjustments
Operating activities
Net income	(39,146)	(18,955)	(129,204)	(85,479)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			0	0
Depreciation and amortization	0	0	0	0
Provision for bad debts			0	0
Equity in earnings of unconsolidated subsidiaries	0	0	0	0
Equity in earnings of consolidated subsidiaries	39,146	18,955	129,204	85,479
Loss on extinguishment of debt			0	0
Loss (gain) on sale of assets and businesses			0	0
Stock compensation expense			0	0
Amortization of debt discount, premium and issuance costs			0	0
Deferred income taxes			0	0
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			0	0
Other current assets			0	0
Other assets			0	0
Accounts payable			0	0
Accrued expenses			0	0
Income taxes			0	0
Net cash provided by (used in) operating activities			0	0
Investing activities
Business combinations, net of cash acquired			0	0
Purchases of property and equipment			0	0
Investment in businesses			0	0
Proceeds from sale of assets and businesses			0	0
Net cash used in investing activities			0	0
Financing activities
Borrowings on revolving facilities			0	0
Payments on revolving facilities			0	0
Proceeds from term loans (financing costs)			0	0
Payments on term loans			0	0
Revolving facility debt issuance costs			0	0
Borrowings of other debt			0	0
Principal payments on other debt			0	0
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			0	0
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			0	0
Distributions to non-controlling interests			0	0
Net cash provided by (used in) financing activities			0	0
Net increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents at beginning of period			0	0
Cash and cash equivalents at end of period	0	0	0	0
Select (Parent Company Only) | Reportable legal entities
Operating activities
Net income	32,917	18,462	113,167	76,387
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			0	0
Depreciation and amortization	2,215	2,355	6,777	5,503
Provision for bad debts			0	0
Equity in earnings of unconsolidated subsidiaries	0	0	0	0
Equity in earnings of consolidated subsidiaries	(36,285)	(18,558)	(111,220)	(75,348)
Loss on extinguishment of debt			115	6,527
Loss (gain) on sale of assets and businesses			(1,641)	(8)
Stock compensation expense			15,059	13,445
Amortization of debt discount, premium and issuance costs			4,435	6,113
Deferred income taxes			1,804	5,014
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			0	0
Other current assets			(2,420)	1,016
Other assets			(4,381)	1,633
Accounts payable			(42)	2,375
Accrued expenses			20,379	164
Income taxes			9,622	3,776
Net cash provided by (used in) operating activities			51,654	46,597
Investing activities
Business combinations, net of cash acquired			0	0
Purchases of property and equipment			(6,412)	(26,350)
Investment in businesses			0	0
Proceeds from sale of assets and businesses			1,654	8
Net cash used in investing activities			(4,758)	(26,342)
Financing activities
Borrowings on revolving facilities			420,000	805,000
Payments on revolving facilities			(585,000)	(705,000)
Proceeds from term loans (financing costs)			(11)	1,139,487
Payments on term loans			(8,625)	(1,153,502)
Revolving facility debt issuance costs			(837)	(4,392)
Borrowings of other debt			5,542	21,572
Principal payments on other debt			(8,455)	(10,122)
Dividends paid to Holdings			(5,640)	(3,603)
Equity investment by Holdings			1,633	1,634
Intercompany			140,673	(101,888)
Decrease in overdrafts			(6,172)	(20,439)
Proceeds from issuance of non-controlling interests			0	0
Distributions to non-controlling interests			0	0
Net cash provided by (used in) financing activities			(46,892)	(31,253)
Net increase (decrease) in cash and cash equivalents			4	(10,998)
Cash and cash equivalents at beginning of period			73	11,071
Cash and cash equivalents at end of period	77	73	77	73
Subsidiary Guarantors | Reportable legal entities
Operating activities
Net income	28,799	13,825	90,539	59,530
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			10,700	14,493
Depreciation and amortization	19,726	18,015	59,708	57,568
Provision for bad debts			(451)	864
Equity in earnings of unconsolidated subsidiaries	(5,424)	(4,416)	(14,884)	(15,555)
Equity in earnings of consolidated subsidiaries	(2,861)	(397)	(17,984)	(10,131)
Loss on extinguishment of debt			0	0
Loss (gain) on sale of assets and businesses			(7,493)	(4,824)
Stock compensation expense			0	0
Amortization of debt discount, premium and issuance costs			0	0
Deferred income taxes			2,527	0
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			37,490	(105,536)
Other current assets			(2,100)	3,857
Other assets			(8,576)	(3,709)
Accounts payable			(5,155)	(823)
Accrued expenses			13,620	(1,175)
Income taxes			4,401	0
Net cash provided by (used in) operating activities			162,342	(5,441)
Investing activities
Business combinations, net of cash acquired			(2,666)	(3,356)
Purchases of property and equipment			(60,669)	(102,342)
Investment in businesses			(12,931)	(11,374)
Proceeds from sale of assets and businesses			5,029	15,007
Net cash used in investing activities			(71,237)	(102,065)
Financing activities
Borrowings on revolving facilities			0	0
Payments on revolving facilities			0	0
Proceeds from term loans (financing costs)			0	0
Payments on term loans			0	0
Revolving facility debt issuance costs			0	0
Borrowings of other debt			0	0
Principal payments on other debt			(540)	(306)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(88,344)	107,834
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			0	0
Distributions to non-controlling interests			(1,450)	(130)
Net cash provided by (used in) financing activities			(90,334)	107,398
Net increase (decrease) in cash and cash equivalents			771	(108)
Cash and cash equivalents at beginning of period			4,856	6,467
Cash and cash equivalents at end of period	5,627	6,359	5,627	6,359
Non-Guarantor Subsidiaries | Reportable legal entities
Operating activities
Net income	4,025	756	27,142	13,737
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			34	49
Depreciation and amortization	4,098	3,388	12,205	10,007
Provision for bad debts			0	0
Equity in earnings of unconsolidated subsidiaries	(8)	(15)	(30)	(63)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Loss on extinguishment of debt			0	0
Loss (gain) on sale of assets and businesses			5	(4,687)
Stock compensation expense			0	0
Amortization of debt discount, premium and issuance costs			0	0
Deferred income taxes			103	0
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(894)	(22,820)
Other current assets			(1,807)	(6,772)
Other assets			1,604	3,044
Accounts payable			3,059	1,580
Accrued expenses			6,412	10,281
Income taxes			1	0
Net cash provided by (used in) operating activities			47,834	4,356
Investing activities
Business combinations, net of cash acquired			(22)	(295)
Purchases of property and equipment			(24,677)	(23,452)
Investment in businesses			0	0
Proceeds from sale of assets and businesses			8	19,537
Net cash used in investing activities			(24,691)	(4,210)
Financing activities
Borrowings on revolving facilities			0	0
Payments on revolving facilities			0	0
Proceeds from term loans (financing costs)			0	0
Payments on term loans			0	0
Revolving facility debt issuance costs			0	0
Borrowings of other debt			19,935	3,232
Principal payments on other debt			(4,504)	(2,150)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(34,184)	(5,946)
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			957	8,986
Distributions to non-controlling interests			(6,863)	(4,776)
Net cash provided by (used in) financing activities			(24,659)	(654)
Net increase (decrease) in cash and cash equivalents			(1,516)	(508)
Cash and cash equivalents at beginning of period			4,561	5,056
Cash and cash equivalents at end of period	3,045	4,548	3,045	4,548
Non-Guarantor Concentra | Reportable legal entities
Operating activities
Net income	16,084	10,736	45,576	35,412
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			0	0
Depreciation and amortization	24,488	15,014	70,332	46,566
Provision for bad debts			78	50
Equity in earnings of unconsolidated subsidiaries	0	0	0	0
Equity in earnings of consolidated subsidiaries	0	0	0	0
Loss on extinguishment of debt			369	0
Loss (gain) on sale of assets and businesses			0	20
Stock compensation expense			2,116	782
Amortization of debt discount, premium and issuance costs			5,410	2,433
Deferred income taxes			(6,526)	(11,140)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(13,101)	(14,952)
Other current assets			(3,947)	(778)
Other assets			16,181	439
Accounts payable			(1,369)	781
Accrued expenses			8,980	9,482
Income taxes			(4,952)	15,365
Net cash provided by (used in) operating activities			119,147	84,460
Investing activities
Business combinations, net of cash acquired			(516,570)	(15,720)
Purchases of property and equipment			(29,281)	(21,656)
Investment in businesses			(5)	0
Proceeds from sale of assets and businesses			0	3
Net cash used in investing activities			(545,856)	(37,373)
Financing activities
Borrowings on revolving facilities			0	0
Payments on revolving facilities			0	0
Proceeds from term loans (financing costs)			779,915	0
Payments on term loans			0	(23,065)
Revolving facility debt issuance costs			(496)	0
Borrowings of other debt			4,657	2,767
Principal payments on other debt			(4,472)	(2,534)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(18,145)	0
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			1,969	0
Distributions to non-controlling interests			(298,114)	(4,370)
Net cash provided by (used in) financing activities			465,314	(27,202)
Net increase (decrease) in cash and cash equivalents			38,605	19,885
Cash and cash equivalents at beginning of period			113,059	76,435
Cash and cash equivalents at end of period	151,664	96,320	151,664	96,320
Select Medical Corporation
Operating activities
Net income	42,679	24,824	147,220	99,587
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			10,734	14,542
Depreciation and amortization	50,527	38,772	149,022	119,644
Provision for bad debts			(373)	914
Equity in earnings of unconsolidated subsidiaries	(5,432)	(4,431)	(14,914)	(15,618)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Loss on extinguishment of debt			484	6,527
Loss (gain) on sale of assets and businesses			(9,129)	(9,499)
Stock compensation expense			17,175	14,227
Amortization of debt discount, premium and issuance costs			9,845	8,546
Deferred income taxes			(2,092)	(6,126)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			23,495	(143,308)
Other current assets			(10,274)	(2,677)
Other assets			4,828	1,407
Accounts payable			(3,507)	3,913
Accrued expenses			49,391	18,752
Income taxes			9,072	19,141
Net cash provided by (used in) operating activities			380,977	129,972
Investing activities
Business combinations, net of cash acquired			(519,258)	(19,371)
Purchases of property and equipment			(121,039)	(173,800)
Investment in businesses			(12,936)	(11,374)
Proceeds from sale of assets and businesses			6,691	34,555
Net cash used in investing activities			(646,542)	(169,990)
Financing activities
Borrowings on revolving facilities			420,000	805,000
Payments on revolving facilities			(585,000)	(705,000)
Proceeds from term loans (financing costs)			779,904	1,139,487
Payments on term loans			(8,625)	(1,176,567)
Revolving facility debt issuance costs			(1,333)	(4,392)
Borrowings of other debt			30,134	27,571
Principal payments on other debt			(17,971)	(15,112)
Dividends paid to Holdings			(5,640)	(3,603)
Equity investment by Holdings			1,633	1,634
Intercompany			0	0
Decrease in overdrafts			(6,172)	(20,439)
Proceeds from issuance of non-controlling interests			2,926	8,986
Distributions to non-controlling interests			(306,427)	(9,276)
Net cash provided by (used in) financing activities			303,429	48,289
Net increase (decrease) in cash and cash equivalents			37,864	8,271
Cash and cash equivalents at beginning of period			122,549	99,029
Cash and cash equivalents at end of period	$ 160,413	$ 107,300	$ 160,413	$ 107,300