GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 186,352	$ 319,399	$ 297,366	$ 306,997
Short-term marketable securities	37,792	38,179
Intercompany receivables	0	0
Accounts receivable, net	551,841	528,924
Other current assets	303,837	267,554
Property, plant and equipment, net	1,631,648	1,587,365
Investments in subsidiaries	0	0
Intercompany debt receivable	0	0
Goodwill	492,705	478,523
Permits and other intangibles, net	464,635	469,128
Other long-term assets	16,006	17,498
Total assets	3,684,816	3,706,570
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	524,684	503,817
Intercompany payables	0	0
Closure, post-closure and remedial liabilities, net	166,704	165,723
Long-term obligations, less current portion	1,625,259	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	222,643	223,291
Total liabilities	2,539,290	2,518,368
Stockholders’ equity	1,145,526	1,188,202
Total liabilities and stockholders’ equity	3,684,816	3,706,570
Reportable Legal Entities | Clean Harbors, Inc.
ASSETS
Cash and cash equivalents	51,781	51,638	51,726	51,417
Short-term marketable securities	0	0
Intercompany receivables	244,228	238,339
Accounts receivable, net	0	0
Other current assets	0	897
Property, plant and equipment, net	0	0
Investments in subsidiaries	3,095,335	3,112,547
Intercompany debt receivable	0	0
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	1,938	2,084
Total assets	3,393,282	3,405,505
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	22,210	16,954
Intercompany payables	600,287	574,812
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	1,625,259	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	0	0
Total liabilities	2,247,756	2,217,303
Stockholders’ equity	1,145,526	1,188,202
Total liabilities and stockholders’ equity	3,393,282	3,405,505
Reportable Legal Entities | Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	99,662	207,777	139,160	155,943
Short-term marketable securities	0	0
Intercompany receivables	600,975	590,100
Accounts receivable, net	457,231	433,042
Other current assets	265,477	233,602
Property, plant and equipment, net	1,249,417	1,174,975
Investments in subsidiaries	535,503	569,568
Intercompany debt receivable	89,947	92,530
Goodwill	431,574	415,641
Permits and other intangibles, net	407,887	408,655
Other long-term assets	12,385	12,064
Total assets	4,150,058	4,137,954
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	382,937	371,135
Intercompany payables	306,401	289,531
Closure, post-closure and remedial liabilities, net	149,316	148,872
Long-term obligations, less current portion	0	0
Intercompany debt payable	21,000	21,000
Other long-term liabilities	201,053	201,086
Total liabilities	1,060,707	1,031,624
Stockholders’ equity	3,089,351	3,106,330
Total liabilities and stockholders’ equity	4,150,058	4,137,954
Reportable Legal Entities | Non-Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	34,909	59,984	106,480	99,637
Short-term marketable securities	37,792	38,179
Intercompany receivables	63,875	52,909
Accounts receivable, net	94,610	95,882
Other current assets	52,050	52,947
Property, plant and equipment, net	382,231	412,390
Investments in subsidiaries	0	0
Intercompany debt receivable	21,000	21,000
Goodwill	61,131	62,882
Permits and other intangibles, net	56,748	60,473
Other long-term assets	1,695	3,350
Total assets	806,041	859,996
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	133,227	135,620
Intercompany payables	2,390	17,005
Closure, post-closure and remedial liabilities, net	17,388	16,851
Long-term obligations, less current portion	0	0
Intercompany debt payable	89,947	92,530
Other long-term liabilities	21,602	22,205
Total liabilities	264,554	284,211
Stockholders’ equity	541,487	575,785
Total liabilities and stockholders’ equity	806,041	859,996
Consolidating Adjustments
ASSETS
Cash and cash equivalents	0	0	$ 0	$ 0
Short-term marketable securities	0	0
Intercompany receivables	(909,078)	(881,348)
Accounts receivable, net	0	0
Other current assets	(13,690)	(19,892)
Property, plant and equipment, net	0	0
Investments in subsidiaries	(3,630,838)	(3,682,115)
Intercompany debt receivable	(110,947)	(113,530)
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	(12)	0
Total assets	(4,664,565)	(4,696,885)
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	(13,690)	(19,892)
Intercompany payables	(909,078)	(881,348)
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	0	0
Intercompany debt payable	(110,947)	(113,530)
Other long-term liabilities	(12)	0
Total liabilities	(1,033,727)	(1,014,770)
Stockholders’ equity	(3,630,838)	(3,682,115)
Total liabilities and stockholders’ equity	$ (4,664,565)	$ (4,696,885)