Condensed Consolidating Financial Information - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net income	$ 60,559	$ 51,300	$ 104,541	$ 74,763
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			7,830	10,933
Depreciation and amortization	51,724	38,333	98,495	80,872
Provision for bad debts		(36)	102	745
Equity in earnings of unconsolidated subsidiaries	(4,785)	(5,666)	(9,482)	(11,187)
Loss on extinguishment of debt			484	6,527
Gain on sale of assets and businesses			(6,980)	(9,523)
Stock compensation expense			10,911	9,270
Amortization of debt discount, premium and issuance costs			6,486	5,974
Deferred income taxes			(1,691)	(1,474)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(5,774)	(140,949)
Other current assets			(3,011)	(5,557)
Other assets			6,684	4,621
Accounts payable			(5,462)	759
Accrued expenses			1,207	(4,833)
Income taxes			12,610	19,399
Net cash provided by (used in) operating activities			216,950	40,340
Investing activities
Business combinations, net of cash acquired			(517,704)	(18,508)
Purchases of property and equipment	(42,031)	(54,649)	(81,648)	(105,302)
Investment in businesses			(3,291)	(9,874)
Proceeds from sale of assets and businesses			6,672	34,552
Net cash provided by (used in) investing activities			(595,971)	(99,132)
Financing activities
Borrowings on revolving facilities			265,000	630,000
Payments on revolving facilities			(345,000)	(550,000)
Proceeds from term loans (financing costs)			779,904	1,139,487
Payments on term loans			(5,750)	(1,173,692)
Revolving facility debt issuance costs			(1,333)	(4,392)
Borrowings of other debt			19,928	9,444
Principal payments on other debt			(11,521)	(10,437)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Decrease in overdrafts			(6,171)	(5,228)
Proceeds from issuance of non-controlling interests			2,926	3,553
Distributions to non-controlling interests			(301,213)	(5,536)
Net cash provided by (used in) financing activities			397,501	33,562
Net increase (decrease) in cash and cash equivalents			18,480	(25,230)
Cash and cash equivalents at beginning of period			122,549	99,029
Cash and cash equivalents at end of period	141,029	73,799	141,029	73,799
Consolidating and Eliminating Adjustments
Operating activities
Net income	(51,350)	(32,723)	(90,058)	(66,524)
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	51,350	32,723	90,058	66,524
Loss on extinguishment of debt			0	0
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 provided by (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	46,511	42,055	80,250	57,925
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			0	0
Depreciation and amortization	2,355	1,573	4,562	3,148
Provision for bad debts			0	0
Equity in earnings of unconsolidated subsidiaries	0	0	0	0
Equity in earnings of consolidated subsidiaries	(44,510)	(28,534)	(74,935)	(56,790)
Loss on extinguishment of debt			115	6,527
Gain on sale of assets and businesses			(1,642)	(8)
Stock compensation expense			9,562	8,700
Amortization of debt discount, premium and issuance costs			3,553	4,342
Deferred income taxes			664	5,987
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			0	0
Other current assets			(876)	(5,631)
Other assets			945	3,184
Accounts payable			(1,470)	(413)
Accrued expenses			(15,020)	(5,618)
Income taxes			14,757	9,366
Net cash provided by (used in) operating activities			20,465	30,719
Investing activities
Business combinations, net of cash acquired			0	0
Purchases of property and equipment			(5,232)	(7,093)
Investment in businesses			0	0
Proceeds from sale of assets and businesses			1,655	8
Net cash provided by (used in) investing activities			(3,577)	(7,085)
Financing activities
Borrowings on revolving facilities			265,000	630,000
Payments on revolving facilities			(345,000)	(550,000)
Proceeds from term loans (financing costs)			(11)	1,139,487
Payments on term loans			(5,750)	(1,150,627)
Revolving facility debt issuance costs			(837)	(4,392)
Borrowings of other debt			5,549	6,572
Principal payments on other debt			(5,987)	(7,353)
Dividends paid to Holdings			(889)	(600)
Equity investment by Holdings			1,620	963
Intercompany			90,589	(93,455)
Decrease in overdrafts			(6,171)	(5,228)
Proceeds from issuance of non-controlling interests			0	0
Distributions to non-controlling interests			0	0
Net cash provided by (used in) financing activities			(1,887)	(34,633)
Net increase (decrease) in cash and cash equivalents			15,001	(10,999)
Cash and cash equivalents at beginning of period			73	11,071
Cash and cash equivalents at end of period	15,074	72	15,074	72
Subsidiary Guarantors | Reportable legal entities
Operating activities
Net income	35,311	22,717	61,740	45,705
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			7,800	10,902
Depreciation and amortization	20,535	18,182	39,982	39,553
Provision for bad debts			41	715
Equity in earnings of unconsolidated subsidiaries	(4,776)	(5,646)	(9,460)	(11,139)
Equity in earnings of consolidated subsidiaries	(6,840)	(4,189)	(15,123)	(9,734)
Loss on extinguishment of debt			0	0
Gain on sale of assets and businesses			(5,338)	(4,828)
Stock compensation expense			0	0
Amortization of debt discount, premium and issuance costs			0	0
Deferred income taxes			1,056	0
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			9,838	(104,767)
Other current assets			1,927	6,047
Other assets			(9,261)	(16,925)
Accounts payable			(7,516)	(1,697)
Accrued expenses			14,589	(4,507)
Income taxes			4,401	0
Net cash provided by (used in) operating activities			94,676	(50,675)
Investing activities
Business combinations, net of cash acquired			(2,666)	(2,305)
Purchases of property and equipment			(44,865)	(72,005)
Investment in businesses			(3,286)	(9,874)
Proceeds from sale of assets and businesses			5,017	15,007
Net cash provided by (used in) investing activities			(45,800)	(69,177)
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			(261)	(204)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(45,661)	119,128
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			0	0
Distributions to non-controlling interests			(1,450)	(6)
Net cash provided by (used in) financing activities			(47,372)	118,918
Net increase (decrease) in cash and cash equivalents			1,504	(934)
Cash and cash equivalents at beginning of period			4,856	6,467
Cash and cash equivalents at end of period	6,360	5,533	6,360	5,533
Non-Guarantor Subsidiaries | Reportable legal entities
Operating activities
Net income	10,253	6,403	23,117	12,981
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			30	31
Depreciation and amortization	4,137	3,149	8,107	6,619
Provision for bad debts			0	0
Equity in earnings of unconsolidated subsidiaries	(9)	(20)	(22)	(48)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Loss on extinguishment of debt			0	0
Gain on sale of assets and businesses			0	(4,687)
Stock compensation expense			0	0
Amortization of debt discount, premium and issuance costs			0	0
Deferred income taxes			40	0
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(6,857)	(22,291)
Other current assets			2,956	(3,112)
Other assets			1,110	17,426
Accounts payable			1,864	137
Accrued expenses			4,914	8,394
Income taxes			1	0
Net cash provided by (used in) operating activities			35,260	15,450
Investing activities
Business combinations, net of cash acquired			(22)	0
Purchases of property and equipment			(14,809)	(9,917)
Investment in businesses			0	0
Proceeds from sale of assets and businesses			0	19,537
Net cash provided by (used in) investing activities			(14,831)	9,620
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			9,820	105
Principal payments on other debt			(2,400)	(1,183)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(27,290)	(25,673)
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			957	3,553
Distributions to non-controlling interests			(1,681)	(1,982)
Net cash provided by (used in) financing activities			(20,594)	(25,180)
Net increase (decrease) in cash and cash equivalents			(165)	(110)
Cash and cash equivalents at beginning of period			4,561	5,056
Cash and cash equivalents at end of period	4,396	4,946	4,396	4,946
Non-Guarantor Concentra | Reportable legal entities
Operating activities
Net income	19,834	12,848	29,492	24,676
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			0	0
Depreciation and amortization	24,697	15,429	45,844	31,552
Provision for bad debts			61	30
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
Gain on sale of assets and businesses			0	0
Stock compensation expense			1,349	570
Amortization of debt discount, premium and issuance costs			2,933	1,632
Deferred income taxes			(3,451)	(7,461)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(8,755)	(13,891)
Other current assets			(7,018)	(2,861)
Other assets			13,890	936
Accounts payable			1,660	2,732
Accrued expenses			(3,276)	(3,102)
Income taxes			(6,549)	10,033
Net cash provided by (used in) operating activities			66,549	44,846
Investing activities
Business combinations, net of cash acquired			(515,016)	(16,203)
Purchases of property and equipment			(16,742)	(16,287)
Investment in businesses			(5)	0
Proceeds from sale of assets and businesses			0	0
Net cash provided by (used in) investing activities			(531,763)	(32,490)
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			4,559	2,767
Principal payments on other debt			(2,873)	(1,697)
Dividends paid to Holdings			0	0
Equity investment by Holdings			0	0
Intercompany			(17,638)	0
Decrease in overdrafts			0	0
Proceeds from issuance of non-controlling interests			1,969	0
Distributions to non-controlling interests			(298,082)	(3,548)
Net cash provided by (used in) financing activities			467,354	(25,543)
Net increase (decrease) in cash and cash equivalents			2,140	(13,187)
Cash and cash equivalents at beginning of period			113,059	76,435
Cash and cash equivalents at end of period	115,199	63,248	115,199	63,248
Select Medical Corporation
Operating activities
Net income	60,559	51,300	104,541	74,763
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Distributions from unconsolidated subsidiaries			7,830	10,933
Depreciation and amortization	51,724	38,333	98,495	80,872
Provision for bad debts			102	745
Equity in earnings of unconsolidated subsidiaries	(4,785)	(5,666)	(9,482)	(11,187)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Loss on extinguishment of debt			484	6,527
Gain on sale of assets and businesses			(6,980)	(9,523)
Stock compensation expense			10,911	9,270
Amortization of debt discount, premium and issuance costs			6,486	5,974
Deferred income taxes			(1,691)	(1,474)
Changes in operating assets and liabilities, net of effects of business combinations:
Accounts receivable			(5,774)	(140,949)
Other current assets			(3,011)	(5,557)
Other assets			6,684	4,621
Accounts payable			(5,462)	759
Accrued expenses			1,207	(4,833)
Income taxes			12,610	19,399
Net cash provided by (used in) operating activities			216,950	40,340
Investing activities
Business combinations, net of cash acquired			(517,704)	(18,508)
Purchases of property and equipment			(81,648)	(105,302)
Investment in businesses			(3,291)	(9,874)
Proceeds from sale of assets and businesses			6,672	34,552
Net cash provided by (used in) investing activities			(595,971)	(99,132)
Financing activities
Borrowings on revolving facilities			265,000	630,000
Payments on revolving facilities			(345,000)	(550,000)
Proceeds from term loans (financing costs)			779,904	1,139,487
Payments on term loans			(5,750)	(1,173,692)
Revolving facility debt issuance costs			(1,333)	(4,392)
Borrowings of other debt			19,928	9,444
Principal payments on other debt			(11,521)	(10,437)
Dividends paid to Holdings			(889)	(600)
Equity investment by Holdings			1,620	963
Intercompany			0	0
Decrease in overdrafts			(6,171)	(5,228)
Proceeds from issuance of non-controlling interests			2,926	3,553
Distributions to non-controlling interests			(301,213)	(5,536)
Net cash provided by (used in) financing activities			397,501	33,562
Net increase (decrease) in cash and cash equivalents			18,480	(25,230)
Cash and cash equivalents at beginning of period			122,549	99,029
Cash and cash equivalents at end of period	$ 141,029	$ 73,799	$ 141,029	$ 73,799