QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net sales	$ 4,005.2	$ 3,998.5	$ 3,985.8	$ 3,751.9	$ 3,938.4	$ 3,958.1	$ 3,852.1	$ 3,571.6	$ 15,741.4	$ 15,320.2	$ 14,187.8
Cost of sales	2,269.1	2,261.5	2,241.0	2,128.1	2,284.4	2,330.5	2,334.8	2,205.2	8,899.7	9,154.9	8,831.0
Selling, general and administrative expenses	1,050.0	1,024.8	1,075.7	1,077.7	1,034.8	1,024.9	1,011.6	990.3	4,228.2	4,061.6	3,653.8
Special (gains) and charges	103.3	(332.6)	12.2	28.2	29.2	36.7	21.0	24.5	(188.9)	111.4	140.5
Operating Income	582.8	1,044.8	656.9	517.9	590.0	566.0	484.7	351.6	2,802.4	1,992.3	1,562.5
Other (income) expense (b)	(13.2)	(12.9)	(12.6)	(12.6)	(17.9)	(14.5)	(14.4)	(13.1)	(51.3)	(59.9)	(24.5)
Interest expense, net	61.7	70.4	78.8	71.6	70.4	74.3	77.8	74.2	282.5	296.7	243.6
Income before income taxes	534.3	987.3	590.7	458.9	537.5	506.2	421.3	290.5	2,571.2	1,755.5	1,343.4
Provision for income taxes	54.8	246.5	95.7	42.3	126.7	96.8	86.6	52.4	439.3	362.5	$ 234.5
Net income from continuing operations including noncontrolling interest	479.5	740.8	495.0	416.6	410.8	409.4	334.7	238.1	2,131.9	1,393.0
Net income from continuing operations attributable to noncontrolling interest	6.6	4.3	4.1	4.5	5.6	5.4	5.0	4.7	19.5	20.7
Net income attributable to Ecolab	$ 472.9	$ 736.5	$ 490.9	$ 412.1	$ 405.2	$ 404.0	$ 329.7	$ 233.4	$ 2,112.4	$ 1,372.3
Basic EPS
Earnings attributable to Ecolab	$ 1.67	$ 2.6	$ 1.72	$ 1.44	$ 1.42	$ 1.42	$ 1.16	$ 0.82	$ 7.43	$ 4.82	$ 3.83
Diluted EPS
Earnings attributable to Ecolab	$ 1.66	$ 2.58	$ 1.71	$ 1.43	$ 1.41	$ 1.41	$ 1.15	$ 0.82	$ 7.37	$ 4.79	$ 3.81
Weighted-average common shares outstanding
Basic (in shares)	283.3	283.6	284.6	285.7	285.3	285.1	284.9	284.6	284.3	285.0	285.2
Diluted (in shares)	285.7	286.0	287.0	287.8	287.1	286.9	286.3	285.9	286.6	286.5	286.6
Cost of sales
Special (gains) and charges									$ 5.3	$ 22.5	$ 69.9
Weighted-average common shares outstanding
Cost of sales, special charges	$ 2.1	$ 0.9	$ 0.7	$ 1.6	$ 5.3	$ 5.9	$ 8.1	$ 3.2
Other (income) expense
Special (gains) and charges											$ 50.6