Earnings Attributable to Ecolab Per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Computations of the basic and diluted earnings attributable to Ecolab per share amounts
Net income attributable to Ecolab	$ 233.4	$ 191.0
Weighted-average common shares outstanding
Basic (in shares)	298.2	300.6
Effect of dilutive stock options, units and awards (in shares)	5.0	5.9
Diluted (in shares)	303.2	306.5
Earnings attributable to Ecolab per common share
Basic (in dollars per share)	$ 0.78us-gaap_EarningsPerShareBasic	$ 0.64us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 0.77us-gaap_EarningsPerShareDiluted	$ 0.62us-gaap_EarningsPerShareDiluted
Anti-dilutive stock options, units and awards excluded from computation of earnings per share (in shares)	1.9	1.8

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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