Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended						4 Months Ended		12 Months Ended
	Sep. 07, 2019	Jun. 15, 2019	Mar. 23, 2019	Sep. 08, 2018	Jun. 16, 2018	Mar. 24, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Revenues
Revenues	$ 104,841	$ 105,000	$ 95,772	$ 99,674	$ 100,303	$ 83,147	$ 138,814	$ 127,059	$ 444,427	$ 410,183	$ 365,957
Rental income	5,657	5,762	3,548	0	0	0	7,696	0	22,663
Operating expenses
Operating costs	80,117	78,849	82,483	76,045	76,272	68,386	108,154	102,462	349,603	323,165	276,102
Selling, general, and administrative expenses	11,241	11,042	12,396	10,641	11,522	11,022	15,545	14,529	50,224	47,714	47,401
Depreciation and amortization	3,980	4,061	4,136	3,776	3,659	3,643	6,072	5,079	18,249	16,157	17,967
Other expense (income) - net	1,021	1,514	(58)	253	341	389	11,013	623	13,490	1,606	(10,940)
Operating income	8,482	9,534	(3,185)	8,959	8,509	(293)	(1,970)	4,366	12,861	21,541	35,427
Interest expense – net	180	219	230	256	240	245	240	310	869	1,052	1,094
Income before income taxes	8,302	9,315	(3,415)	8,703	8,269	(538)	(2,210)	4,056	11,992	20,489	34,333
Provision for income taxes	2,246	2,151	(986)	2,284	2,149	(436)	(168)	1,455	3,243	5,451	5,923
Net income	6,056	7,164	(2,429)	6,419	6,120	(102)	(2,042)	2,601	8,749	15,038	28,410
Income attributable to noncontrolling interest	87	108	83	74	121	18	108	97	386	310	287
Income attributable to Heritage-Crystal Clean, Inc. common stockholders	$ 5,969	$ 7,056	$ (2,512)	$ 6,345	$ 5,999	$ (120)	$ (2,150)	$ 2,504	$ 8,363	$ 14,728	$ 28,123
Net income per share: basic (in dollars per share)	$ 0.26	$ 0.30	$ (0.11)	$ 0.28	$ 0.26	$ (0.01)	$ (0.09)	$ 0.11	$ 0.36	$ 0.64	$ 1.24
Net income per share: diluted (in dollars per share)	$ 0.25	$ 0.30	$ (0.11)	$ 0.27	$ 0.26	$ (0.01)	$ (0.09)	$ 0.11	$ 0.36	$ 0.63	$ 1.23
Number of weighted average shares outstanding: basic	23,185	23,137	23,117	23,048	23,029	22,962	23,190	23,056	23,160	23,026	22,662
Number of weighted average shares outstanding: diluted	23,421	23,368	23,117	23,404	23,361	22,962	23,190	23,411	23,398	23,334	22,922
Service revenues
Revenues
Revenues	$ 57,220	$ 57,936	$ 56,366	$ 58,054	$ 60,014	$ 54,137	$ 78,969	$ 78,057	$ 250,491	$ 250,262	$ 233,999
Product revenues
Revenues
Revenues	$ 41,964	$ 41,302	$ 35,858	$ 41,620	$ 40,289	$ 29,010	$ 52,149	$ 49,002	$ 171,273	$ 159,921	$ 131,958