GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 197,068	$ 319,399	$ 446,366	$ 306,997
Short-term marketable securities	36,862	38,179
Intercompany receivables	0	0
Accounts receivable, net	590,580	528,924
Other current assets	311,972	267,554
Property, plant and equipment, net	1,609,382	1,587,365
Investments in subsidiaries	0	0
Intercompany debt receivable	0	0
Goodwill	497,251	478,523
Permits and other intangibles, net	455,920	469,128
Other long-term assets	16,426	17,498
Total assets	3,715,461	3,706,570
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	543,668	503,817
Intercompany payables	0	0
Closure, post-closure and remedial liabilities, net	163,772	165,723
Long-term obligations, less current portion	1,624,727	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	222,246	223,291
Total liabilities	2,554,413	2,518,368
Stockholders’ equity	1,161,048	1,188,202
Total liabilities and stockholders’ equity	3,715,461	3,706,570
Reportable Legal Entities | Clean Harbors, Inc.
ASSETS
Cash and cash equivalents	51,960	51,638	51,391	51,417
Short-term marketable securities	0	0
Intercompany receivables	250,206	238,339
Accounts receivable, net	0	0
Other current assets	0	897
Property, plant and equipment, net	0	0
Investments in subsidiaries	3,135,271	3,112,547
Intercompany debt receivable	0	0
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	2,283	2,084
Total assets	3,439,720	3,405,505
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	16,627	16,954
Intercompany payables	637,318	574,812
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	1,624,727	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	0	0
Total liabilities	2,278,672	2,217,303
Stockholders’ equity	1,161,048	1,188,202
Total liabilities and stockholders’ equity	3,439,720	3,405,505
Reportable Legal Entities | Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	92,833	207,777	303,996	155,943
Short-term marketable securities	0	0
Intercompany receivables	651,218	590,100
Accounts receivable, net	497,775	433,042
Other current assets	260,489	233,602
Property, plant and equipment, net	1,243,171	1,174,975
Investments in subsidiaries	599,091	569,568
Intercompany debt receivable	15,224	92,530
Goodwill	437,229	415,641
Permits and other intangibles, net	402,096	408,655
Other long-term assets	12,337	12,064
Total assets	4,211,463	4,137,954
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	406,111	371,135
Intercompany payables	309,423	289,531
Closure, post-closure and remedial liabilities, net	146,922	148,872
Long-term obligations, less current portion	0	0
Intercompany debt payable	21,000	21,000
Other long-term liabilities	200,999	201,086
Total liabilities	1,084,455	1,031,624
Stockholders’ equity	3,127,008	3,106,330
Total liabilities and stockholders’ equity	4,211,463	4,137,954
Reportable Legal Entities | Non-Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	52,275	59,984	90,979	99,637
Short-term marketable securities	36,862	38,179
Intercompany receivables	61,125	52,909
Accounts receivable, net	92,805	95,882
Other current assets	60,225	52,947
Property, plant and equipment, net	366,211	412,390
Investments in subsidiaries	0	0
Intercompany debt receivable	21,000	21,000
Goodwill	60,022	62,882
Permits and other intangibles, net	53,824	60,473
Other long-term assets	1,811	3,350
Total assets	806,160	859,996
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	129,672	135,620
Intercompany payables	15,808	17,005
Closure, post-closure and remedial liabilities, net	16,850	16,851
Long-term obligations, less current portion	0	0
Intercompany debt payable	15,224	92,530
Other long-term liabilities	21,252	22,205
Total liabilities	198,806	284,211
Stockholders’ equity	607,354	575,785
Total liabilities and stockholders’ equity	806,160	859,996
Consolidating Adjustments
ASSETS
Cash and cash equivalents	0	0	$ 0	$ 0
Short-term marketable securities	0	0
Intercompany receivables	(962,549)	(881,348)
Accounts receivable, net	0	0
Other current assets	(8,742)	(19,892)
Property, plant and equipment, net	0	0
Investments in subsidiaries	(3,734,362)	(3,682,115)
Intercompany debt receivable	(36,224)	(113,530)
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	(5)	0
Total assets	(4,741,882)	(4,696,885)
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	(8,742)	(19,892)
Intercompany payables	(962,549)	(881,348)
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	0	0
Intercompany debt payable	(36,224)	(113,530)
Other long-term liabilities	(5)	0
Total liabilities	(1,007,520)	(1,014,770)
Stockholders’ equity	(3,734,362)	(3,682,115)
Total liabilities and stockholders’ equity	$ (4,741,882)	$ (4,696,885)