EARNINGS ATTRIBUTABLE TO ECOLAB PER COMMON SHARE ("EPS") (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Computations of the basic and diluted earnings attributable to Ecolab per share amounts
Net income from continuing operations attributable to Ecolab	$ 324.5	$ 246.2	$ 828.9	$ 667.1
Net loss from discontinued operations, net of tax (Note 4) (d)				(2,172.5)
Net income (loss) attributable to Ecolab	$ 324.5	$ 246.2	$ 828.9	$ (1,505.4)
Weighted-average common shares outstanding
Basic (in shares)	286.4	285.4	286.1	287.5
Effect of dilutive stock options and units (in shares)	2.8	3.0	2.9	3.3
Diluted (in shares)	289.2	288.4	289.0	290.8
Basic EPS
Continuing operations	$ 1.13	$ 0.86	$ 2.90	$ 2.32
Discontinued operations				(7.56)
Earnings attributable to Ecolab	1.13	0.86	2.90	(5.24)
Diluted EPS
Continuing operations	1.12	0.85	2.87	2.29
Discontinued operations				(7.47)
Earnings attributable to Ecolab	$ 1.12	$ 0.85	$ 2.87	$ (5.18)
Anti-dilutive securities excluded from the computation of diluted EPS	1.0	1.0	1.0	1.0