Financial Information for Subsidiary Guarantors and Non-Guarantor Subsidiaries under Select's 6.375% Senior Notes - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 122,549	$ 99,029	$ 14,435	$ 3,354
Accounts receivable, net	691,732	573,752
Prepaid income taxes	31,387	12,423
Other current assets	75,158	77,699
Total Current Assets	920,826	762,903
Property and equipment, net	912,591	892,217
Goodwill	2,782,812	2,751,000	2,314,624
Identifiable intangible assets, net	326,519	340,562
Other assets	184,418	173,944
Total Assets	5,127,166	4,920,626	4,388,678
Current Liabilities:
Overdrafts	29,463	39,362
Current portion of long-term debt and notes payable	22,187	13,656
Accounts payable	128,194	126,558
Accrued payroll	160,562	146,397
Accrued vacation	92,875	83,261
Accrued interest	19,885	22,325
Accrued other	143,166	140,076
Income taxes payable	9,071	0
Total Current Liabilities	605,403	571,635
Long-term debt, net of current portion	2,677,715	2,685,333
Non-current deferred tax liability	124,917	199,078
Other non-current liabilities	145,709	136,520
Total Liabilities	3,553,744	3,592,566
Redeemable non-controlling interests	640,818	422,159	238,221	10,985
Stockholder’s Equity:
Common stock	134	132
Capital in excess of par	463,499	443,908
Retained earnings (accumulated deficit)	359,735	371,685
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	823,368	815,725
Non-controlling interests	109,236	90,176
Total Equity	932,604	905,901	908,517	775,240
Total Liabilities and Equity	5,127,166	4,920,626
Eliminations
Current Assets:
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Intercompany receivables	(1,658,682)	(1,599,538)
Prepaid income taxes	0	0
Other current assets	0	0
Total Current Assets	(1,658,682)	(1,599,538)
Property and equipment, net	0	0
Investment in affiliates	(4,650,184)	(4,582,972)
Goodwill	0	0
Identifiable intangible assets, net	0	0
Other assets	(9,989)	(26,684)
Total Assets	(6,318,855)	(6,209,194)
Current Liabilities:
Overdrafts	0	0
Current portion of long-term debt and notes payable	0	0
Accounts payable	0	0
Intercompany payables	(1,658,682)	(1,599,538)
Accrued payroll	0	0
Accrued vacation	0	0
Accrued interest	0	0
Accrued other	0	0
Income taxes payable	0
Total Current Liabilities	(1,658,682)	(1,599,538)
Long-term debt, net of current portion	0	0
Non-current deferred tax liability	(9,989)	(26,684)
Other non-current liabilities	0	0
Total Liabilities	(1,668,671)	(1,626,222)
Redeemable non-controlling interests	624,548	406,666
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	0	0
Retained earnings (accumulated deficit)	(1,447,236)	(1,238,906)
Subsidiary investment	(3,932,822)	(3,837,559)
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	(5,380,058)	(5,076,465)
Non-controlling interests	105,326	86,827
Total Equity	(5,274,732)	(4,989,638)
Total Liabilities and Equity	(6,318,855)	(6,209,194)
Select (Parent Company Only) | Reportable legal entities
Current Assets:
Cash and cash equivalents	73	11,071	4,070	70
Accounts receivable, net	0	0
Intercompany receivables	0	0
Prepaid income taxes	22,704	6,658
Other current assets	13,021	11,953
Total Current Assets	35,798	29,682
Property and equipment, net	39,836	48,697
Investment in affiliates	4,521,865	4,493,684
Goodwill	0	0
Identifiable intangible assets, net	0	0
Other assets	36,494	45,636
Total Assets	4,633,993	4,617,699
Current Liabilities:
Overdrafts	29,463	39,362
Current portion of long-term debt and notes payable	16,635	7,227
Accounts payable	12,504	10,775
Intercompany payables	1,595,692	1,573,960
Accrued payroll	16,736	16,963
Accrued vacation	4,083	3,440
Accrued interest	17,479	20,114
Accrued other	39,219	39,155
Income taxes payable	0
Total Current Liabilities	1,731,811	1,710,996
Long-term debt, net of current portion	2,042,555	2,048,154
Non-current deferred tax liability	0	0
Other non-current liabilities	36,259	42,824
Total Liabilities	3,810,625	3,801,974
Redeemable non-controlling interests	0	0
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	947,370	925,111
Retained earnings (accumulated deficit)	(124,002)	(109,386)
Subsidiary investment	0	0
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	823,368	815,725
Non-controlling interests	0	0
Total Equity	823,368	815,725
Total Liabilities and Equity	4,633,993	4,617,699
Subsidiary Guarantors | Reportable legal entities
Current Assets:
Cash and cash equivalents	4,856	6,467	3,706	2,454
Accounts receivable, net	445,942	363,470
Intercompany receivables	1,595,692	1,573,960
Prepaid income taxes	5,703	0
Other current assets	29,547	33,958
Total Current Assets	2,081,740	1,977,855
Property and equipment, net	622,445	603,408
Investment in affiliates	128,319	89,288
Goodwill	2,108,270	2,090,963
Identifiable intangible assets, net	103,913	106,439
Other assets	98,492	84,803
Total Assets	5,143,179	4,952,756
Current Liabilities:
Overdrafts	0	0
Current portion of long-term debt and notes payable	740	445
Accounts payable	85,096	78,608
Intercompany payables	62,990	25,578
Accrued payroll	98,834	92,216
Accrued vacation	58,043	55,486
Accrued interest	7	0
Accrued other	57,121	62,384
Income taxes payable	1,190
Total Current Liabilities	364,021	314,717
Long-term debt, net of current portion	127	601
Non-current deferred tax liability	88,376	133,852
Other non-current liabilities	56,718	53,537
Total Liabilities	509,242	502,707
Redeemable non-controlling interests	0	0
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	0	0
Retained earnings (accumulated deficit)	1,415,978	1,269,009
Subsidiary investment	3,217,959	3,181,040
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	4,633,937	4,450,049
Non-controlling interests	0	0
Total Equity	4,633,937	4,450,049
Total Liabilities and Equity	5,143,179	4,952,756
Non-Guarantor Subsidiaries | Reportable legal entities
Current Assets:
Cash and cash equivalents	4,561	5,056	625	830
Accounts receivable, net	126,279	97,770
Intercompany receivables	62,990	25,578
Prepaid income taxes	31	0
Other current assets	13,693	10,269
Total Current Assets	207,554	138,673
Property and equipment, net	79,653	50,869
Investment in affiliates	0	0
Goodwill	0	0
Identifiable intangible assets, net	5,200	2,693
Other assets	35,523	53,954
Total Assets	327,930	246,189
Current Liabilities:
Overdrafts	0	0
Current portion of long-term debt and notes payable	2,212	1,324
Accounts payable	17,868	22,397
Intercompany payables	0	0
Accrued payroll	4,872	4,246
Accrued vacation	12,607	10,668
Accrued interest	6	0
Accrued other	12,856	4,639
Income taxes payable	142
Total Current Liabilities	50,563	43,274
Long-term debt, net of current portion	24,730	9,685
Non-current deferred tax liability	780	596
Other non-current liabilities	8,141	5,727
Total Liabilities	84,214	59,282
Redeemable non-controlling interests	0	0
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	0	0
Retained earnings (accumulated deficit)	(33,368)	(32,826)
Subsidiary investment	277,084	219,733
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	243,716	186,907
Non-controlling interests	0	0
Total Equity	243,716	186,907
Total Liabilities and Equity	327,930	246,189
Non-Guarantor Concentra | Reportable legal entities
Current Assets:
Cash and cash equivalents	113,059	76,435	6,034	0
Accounts receivable, net	119,511	112,512
Intercompany receivables	0	0
Prepaid income taxes	2,949	5,765
Other current assets	18,897	21,519
Total Current Assets	254,416	216,231
Property and equipment, net	170,657	189,243
Investment in affiliates	0	0
Goodwill	674,542	660,037
Identifiable intangible assets, net	217,406	231,430
Other assets	23,898	16,235
Total Assets	1,340,919	1,313,176
Current Liabilities:
Overdrafts	0	0
Current portion of long-term debt and notes payable	2,600	4,660
Accounts payable	12,726	14,778
Intercompany payables	0	0
Accrued payroll	40,120	32,972
Accrued vacation	18,142	13,667
Accrued interest	2,393	2,211
Accrued other	33,970	33,898
Income taxes payable	7,739
Total Current Liabilities	117,690	102,186
Long-term debt, net of current portion	610,303	626,893
Non-current deferred tax liability	45,750	91,314
Other non-current liabilities	44,591	34,432
Total Liabilities	818,334	854,825
Redeemable non-controlling interests	16,270	15,493
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	0	0
Retained earnings (accumulated deficit)	64,626	2,723
Subsidiary investment	437,779	436,786
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	502,405	439,509
Non-controlling interests	3,910	3,349
Total Equity	506,315	442,858
Total Liabilities and Equity	1,340,919	1,313,176
Select
Current Assets:
Cash and cash equivalents	122,549	99,029	14,435	3,354
Accounts receivable, net	691,732	573,752
Intercompany receivables	0	0
Prepaid income taxes	31,387	12,423
Other current assets	75,158	77,699
Total Current Assets	920,826	762,903
Property and equipment, net	912,591	892,217
Investment in affiliates	0	0
Goodwill	2,782,812	2,751,000
Identifiable intangible assets, net	326,519	340,562
Other assets	184,418	173,944
Total Assets	5,127,166	4,920,626
Current Liabilities:
Overdrafts	29,463	39,362
Current portion of long-term debt and notes payable	22,187	13,656
Accounts payable	128,194	126,558
Intercompany payables	0	0
Accrued payroll	160,562	146,397
Accrued vacation	92,875	83,261
Accrued interest	19,885	22,325
Accrued other	143,166	140,076
Income taxes payable	9,071
Total Current Liabilities	605,403	571,635
Long-term debt, net of current portion	2,677,715	2,685,333
Non-current deferred tax liability	124,917	199,078
Other non-current liabilities	145,709	136,520
Total Liabilities	3,553,744	3,592,566
Redeemable non-controlling interests	640,818	422,159	238,221	10,985
Stockholder’s Equity:
Common stock	0	0
Capital in excess of par	947,370	925,111
Retained earnings (accumulated deficit)	(124,002)	(109,386)
Subsidiary investment	0	0
Total Select Medical Holdings Corporation and Select Medical Corporation Stockholders’ Equity	823,368	815,725
Non-controlling interests	109,236	90,176
Total Equity	932,604	905,901	$ 908,517	$ 775,240
Total Liabilities and Equity	$ 5,127,166	$ 4,920,626