CONSOLIDATED STATEMENT OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED STATEMENT OF INCOME
Net sales	$ 3,352.1	$ 3,386.1	$ 3,317.2	$ 3,097.4	$ 3,412.0	$ 3,446.4	$ 3,389.1	$ 3,297.6	$ 13,152.8	$ 13,545.1	$ 14,280.5
Cost of sales including special charges (a)	1,745.1	1,737.2	1,785.2	1,631.4	1,831.7	1,820.0	1,806.5	1,765.3	6,898.9	7,223.5	7,679.1
Selling, general and administrative expenses	1,046.3	1,071.6	1,093.3	1,088.2	1,058.8	1,070.7	1,079.2	1,136.8	4,299.4	4,345.5	4,577.6
Special (gains) and charges	3.8	3.2	26.2	6.3	198.7	142.7	65.6	7.8	39.5	414.8	68.8
Operating income	556.9	574.1	412.5	371.5	322.8	413.0	437.8	387.7	1,915.0	1,561.3	1,955.0
Interest expense, net	68.3	64.9	65.3	66.1	62.3	57.6	61.2	62.5	264.6	243.6	256.6
Income before income taxes	488.6	509.2	347.2	305.4	260.5	355.4	376.6	325.2	1,650.4	1,317.7	1,698.4
Provision for income taxes	116.6	129.7	83.6	73.4	37.6	105.3	67.8	89.8	403.3	300.5	476.2
Net income including noncontrolling interest	372.0	379.5	263.6	232.0	222.9	250.1	308.8	235.4	1,247.1	1,017.2	1,222.2
Net income attributable to noncontrolling interest (including special charges (a))	5.7	5.4	5.2	1.2	14.0	(7.7)	6.8	2.0	17.5	15.1	19.4
Net income attributable to Ecolab	$ 366.3	$ 374.1	$ 258.4	$ 230.8	$ 208.9	$ 257.8	$ 302.0	$ 233.4	$ 1,229.6	$ 1,002.1	$ 1,202.8
Earnings attributable to Ecolab per common share
Basic (in dollars per share)	$ 1.26	$ 1.28	$ 0.88	$ 0.78	$ 0.71	$ 0.87	$ 1.02	$ 0.78	$ 4.20	$ 3.38	$ 4.01
Diluted (in dollars per share)	$ 1.24	$ 1.27	$ 0.87	$ 0.77	$ 0.69	$ 0.86	$ 1.00	$ 0.77	4.14	3.32	3.93
Dividends declared per common share (in dollars per share)									$ 1.420	$ 1.340	$ 1.155
Weighted-average common shares outstanding
Basic (in shares)	291.7	291.6	292.4	294.4	295.8	295.2	296.2	298.2	292.5	296.4	300.1
Diluted (in shares)	295.5	295.7	296.5	298.3	300.6	300.0	301.1	303.2	296.7	301.4	305.9