CONSOLIDATED STATEMENT OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 3,747.2	$ 3,564.5	$ 10,907.7	$ 10,186.9	$ 13,835.9
Cost of sales (including special charges of (a))	2,200.2	2,064.6	6,438.4	5,961.8
Selling, general and administrative expenses	955.2	930.9	2,990.5	2,836.3
Special (gains) and charges	75.6	4.9	113.7	47.9
Operating income	516.2	564.1	1,365.1	1,340.9	1,950.1
Other (income)/expense	(21.0)	(16.9)	(60.0)	(50.5)
Interest expense, net	55.7	55.1	168.4	177.2
Income before income taxes	481.5	525.9	1,256.7	1,214.2
Provision for income taxes	43.2	129.3	216.6	264.0
Net income including noncontrolling interest	438.3	396.6	1,040.1	950.2	$ 1,518.6	$ 1,246.5
Net income attributable to noncontrolling interest	2.9	3.4	6.1	8.2
Net income attributable to Ecolab	$ 435.4	$ 393.2	$ 1,034.0	$ 942.0
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
Dividends declared per common share (in dollars per share)	$ 0.410	$ 0.370	$ 1.230	$ 1.110
Weighted-average common shares outstanding
Basic (in shares)	288.8	289.0	288.8	289.8
Diluted (in shares)	293.4	293.4	293.1	294.2
Product and equipment
Net sales	$ 3,090.3	$ 2,931.9	$ 8,985.7	$ 8,376.9
Cost of sales (including special charges of (a))	1,811.4	1,676.9	5,259.9	4,834.2
Service and lease
Net sales	656.9	632.6	1,922.0	1,810.0
Cost of sales (including special charges of (a))	$ 388.8	$ 387.7	$ 1,178.5	$ 1,127.6