QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net sales	$ 3,938.4	$ 3,958.1	$ 3,852.1	$ 3,571.6	$ 3,671.2	$ 3,669.3	$ 3,580.6	$ 3,266.7	$ 15,320.2	$ 14,187.8	$ 12,733.1
Cost of sales	2,284.4	2,330.5	2,334.8	2,205.2	2,254.9	2,291.6	2,211.1	2,073.4	9,154.9	8,831.0	7,615.8
Selling, general and administrative expenses	1,034.8	1,024.9	1,011.6	990.3	922.1	876.9	940.1	914.7	4,061.6	3,653.8	3,416.1
Special (gains) and charges	29.2	36.7	21.0	24.5	95.0	17.8	3.6	24.1	111.4	140.5	102.6
Operating Income	590.0	566.0	484.7	351.6	399.2	483.0	425.8	254.5	1,992.3	1,562.5	1,598.6
Other (income) expense (b)	(17.9)	(14.5)	(14.4)	(13.1)	8.1	5.7	(19.5)	(18.8)	(59.9)	(24.5)	(33.9)
Interest expense, net	70.4	74.3	77.8	74.2	69.5	65.1	56.0	53.0	296.7	243.6	218.3
Income before income taxes	537.5	506.2	421.3	290.5	321.6	412.2	389.3	220.3	1,755.5	1,343.4	1,414.2
Provision for income taxes	126.7	96.8	86.6	52.4	52.1	60.2	76.6	45.6	362.5	234.5	$ 270.2
Net income from continuing operations including noncontrolling interest	410.8	409.4	334.7	238.1	269.5	352.0	312.7	174.7	1,393.0	1,108.9
Net income from continuing operations attributable to noncontrolling interest	5.6	5.4	5.0	4.7	5.1	4.9	4.4	2.8	20.7	17.2
Net income attributable to Ecolab	$ 405.2	$ 404.0	$ 329.7	$ 233.4	$ 264.4	$ 347.1	$ 308.3	$ 171.9	$ 1,372.3	$ 1,091.7
Basic EPS
Earnings attributable to Ecolab	$ 1.42	$ 1.42	$ 1.16	$ 0.82	$ 0.93	$ 1.22	$ 1.08	$ 0.60	$ 4.82	$ 3.83	$ 3.95
Diluted EPS
Earnings attributable to Ecolab	$ 1.41	$ 1.41	$ 1.15	$ 0.82	$ 0.93	$ 1.21	$ 1.08	$ 0.60	$ 4.79	$ 3.81	$ 3.91
Weighted-average common shares outstanding
Basic (in shares)	285.3	285.1	284.9	284.6	284.6	284.9	285.1	286.2	285.0	285.2	286.3
Diluted (in shares)	287.1	286.9	286.3	285.9	285.8	286.3	286.6	288.1	286.5	286.6	289.1
Cost of sales
Special (gains) and charges									$ 22.5	$ 69.9	$ 93.9
Weighted-average common shares outstanding
Cost of sales, special charges	$ 5.3	$ 5.9	$ 8.1	$ 3.2	$ 8.2	$ 7.1	$ 1.7	$ 52.9
Other (income) expense
Special (gains) and charges					$ 25.8	$ 24.8				$ 50.6	$ 37.2