CONSOLIDATED STATEMENT OF EQUITY - USD ($) shares in Millions, $ in Millions	Ecolab Shareholders Equity Cumulative Effect, Period of Adoption, Adjustment	Ecolab Shareholders Equity	Common Stock	Additional Paid-in Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	OCI (Loss)	Treasury Stock	Non-Controlling Interest	Cumulative Effect, Period of Adoption, Adjustment	Total
Balance at Dec. 31, 2019	$ (4.3)	$ 8,685.3	$ 359.6	$ 5,907.1	$ (4.3)	$ 9,993.7	$ (2,089.7)	$ (5,485.4)	$ 40.5	$ (4.3)	$ 8,725.8
Increase (Decrease) in Stockholders' Equity
Net (loss) income		(1,505.3)				(1,505.3)			14.9		(1,490.4)
Other comprehensive income (loss) activity		143.8					143.8		1.3		145.1
Cash dividends declared		(404.2)				(404.2)			(16.2)		(420.4)
Separation of ChampionX		(1,059.9)		(8.5)				(1,051.4)	3.4		(1,056.5)
Changes in noncontrolling interest		17.6		17.6					(9.2)		8.4
Stock options and awards		266.3	2.5	261.1				2.7			266.3
Reacquired shares		(124.6)						(124.6)			(124.6)
Balance at Sep. 30, 2020		6,014.7	362.1	6,177.3		8,079.9	(1,945.9)	(6,658.7)	34.7		6,049.4
Balance at Dec. 31, 2019	$ (4.3)	8,685.3	359.6	5,907.1	$ (4.3)	9,993.7	(2,089.7)	(5,485.4)	40.5	$ (4.3)	8,725.8
Balance at Dec. 31, 2020		6,166.5	362.6	6,235.0		8,243.0	(1,994.4)	(6,679.7)	35.0		$ 6,201.5
Balance (in shares) at Dec. 31, 2020											285.7
Balance at Jun. 30, 2020		5,855.2	362.0	6,155.0		7,967.8	(1,989.7)	(6,639.9)	35.0		$ 5,890.2
Increase (Decrease) in Stockholders' Equity
Net (loss) income		246.3				246.3			3.0		249.3
Other comprehensive income (loss) activity		43.8					43.8		1.1		44.9
Cash dividends declared		(134.2)				(134.2)			(4.4)		(138.6)
Stock options and awards		23.5	0.1	22.3				1.1			23.5
Reacquired shares		(19.9)						(19.9)			(19.9)
Balance at Sep. 30, 2020		6,014.7	362.1	6,177.3		8,079.9	(1,945.9)	(6,658.7)	34.7		6,049.4
Increase (Decrease) in Stockholders' Equity
Retained earnings											8,243.0
Balance at Dec. 31, 2020		6,166.5	362.6	6,235.0		8,243.0	(1,994.4)	(6,679.7)	35.0		6,201.5
Increase (Decrease) in Stockholders' Equity
Net (loss) income		828.9				828.9			9.8		838.7
Other comprehensive income (loss) activity		260.9					260.9		(1.8)		259.1
Cash dividends declared		(412.1)				(412.1)			(14.7)		(426.8)
Stock options and awards		167.1	1.1	164.8				1.2			167.1
Reacquired shares		(77.8)						(77.8)			(77.8)
Balance at Sep. 30, 2021		6,933.5	363.7	6,399.8		8,659.8	(1,733.5)	(6,756.3)	28.3		$ 6,961.8
Balance (in shares) at Sep. 30, 2021											286.6
Balance at Jun. 30, 2021		6,709.1	363.2	6,333.3		8,472.8	(1,710.6)	(6,749.6)	27.2		$ 6,736.3
Increase (Decrease) in Stockholders' Equity
Net (loss) income		324.5				324.5			4.1		328.6
Other comprehensive income (loss) activity		(22.9)					(22.9)		(0.4)		(23.3)
Cash dividends declared		(137.5)				(137.5)			(2.6)		(140.1)
Stock options and awards		67.4	0.5	66.5				0.4			67.4
Reacquired shares		(7.1)						(7.1)			(7.1)
Balance at Sep. 30, 2021		$ 6,933.5	$ 363.7	$ 6,399.8		$ 8,659.8	$ (1,733.5)	$ (6,756.3)	$ 28.3		$ 6,961.8
Balance (in shares) at Sep. 30, 2021											286.6
Increase (Decrease) in Stockholders' Equity
Retained earnings											$ 8,659.8