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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Computations of the basic and diluted earnings attributable to Ecolab per share amounts
Net income attributable to Ecolab	$ 435.4	$ 393.2	$ 1,034.0	$ 942.0
Weighted-average common shares outstanding
Basic (in shares)	288.8	289.0	288.8	289.8
Effect of dilutive stock options and units (in shares)	4.6	4.4	4.3	4.4
Diluted (in shares)	293.4	293.4	293.1	294.2
Earnings attributable to Ecolab per common share
Basic (in dollars per share)	$ 1.51	$ 1.36	$ 3.58	$ 3.25
Diluted (in dollars per share)	$ 1.48	$ 1.34	$ 3.53	$ 3.20
Anti-dilutive securities excluded from the computation of EPS	1.4	0.1	1.4	1.7