SIGNIFICANT ACCOUNTING POLICIES - Earnings Per Common Share (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
Computations of the basic and diluted earnings attributable to Ecolab per share amounts
Net income (loss) attributable to Ecolab									$ 1,372.3	$ 1,091.7	$ 1,129.9
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
Effect of dilutive stock options and units (in shares)									1.6	1.4	2.8
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
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
Anti-dilutive securities excluded from computation of earnings per share (in shares)									4.3	3.9	1.9