CONSOLIDATED STATEMENT OF EQUITY - USD ($) shares in Millions, $ in Millions	Ecolab Shareholders Equity	Common Stock	Additional Paid-in Capital	Retained Earnings	OCI (Loss)	Treasury Stock	Non-Controlling Interest	Total
Balance at Dec. 31, 2015	$ 6,909.9	$ 350.3	$ 5,086.1	$ 6,160.3	$ (1,423.3)	$ (3,263.5)	$ 70.5	$ 6,980.4
Increase (Decrease) in Stockholders' Equity
New accounting guidance adoption	(29.3)			(29.3)				(29.3)
Net income	1,229.0			1,229.0			17.5	1,246.5
Comprehensive income (loss) activity	(289.6)				(289.6)		(1.3)	(290.9)
Cash dividends declared	(414.9)			(414.9)			(16.9)	(431.8)
Stock options and awards	205.7	2.3	200.2			3.2		205.7
Reacquired shares	(739.6)		(15.5)			(724.1)		(739.6)
Balance at Dec. 31, 2016	6,871.2	352.6	5,270.8	6,945.1	(1,712.9)	(3,984.4)	69.8	6,941.0
Increase (Decrease) in Stockholders' Equity
New accounting guidance adoption	1.9			1.9				1.9
Net income	1,504.6			1,504.6			14.0	1,518.6
Comprehensive income (loss) activity	69.5				69.5		1.7	71.2
Cash dividends declared	(440.0)			(440.0)			(19.3)	(459.3)
Acquisition of noncontrolling interests							4.0	4.0
Stock options and awards	176.7	2.1	170.3			4.3		176.7
Reacquired shares	(600.3)		(5.4)			(594.9)		(600.3)
Balance at Dec. 31, 2017	7,583.6	354.7	5,435.7	8,011.6	(1,643.4)	(4,575.0)	70.2	$ 7,653.8
Balance (in shares) at Dec. 31, 2017								289.3
Increase (Decrease) in Stockholders' Equity
New accounting guidance adoption	(43.6)			(43.6)				$ (43.6)
Net income	247.3			247.3			0.9	248.2
Comprehensive income (loss) activity	85.1				85.1		2.5	87.6
Cash dividends declared	(118.3)			(118.3)			(4.7)	(123.0)
Stock options and awards	62.0	0.8	60.8			0.4		62.0
Reacquired shares	(215.1)					(215.1)		(215.1)
Balance at Mar. 31, 2018	$ 7,601.0	$ 355.5	$ 5,496.5	$ 8,097.0	$ (1,558.3)	$ (4,789.7)	$ 68.9	$ 7,669.9
Balance (in shares) at Mar. 31, 2018								288.5