Earnings Attributable to Ecolab Per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Computations of the basic and diluted earnings attributable to Ecolab per share amounts
Net income attributable to Ecolab	$ 159.6	$ 49.7
Weighted-average common shares outstanding
Basic (in shares)	295.4	291.5
Effect of dilutive stock options, units and awards (in shares)	5.5	6.4
Diluted (in shares)	300.9	297.9
Earnings attributable to Ecolab per common share
Basic (in dollars per share)	$ 0.54	$ 0.17
Diluted (in dollars per share)	$ 0.53	$ 0.17
Anti-dilutive securities excluded from computation of earnings per share (in shares)	2.7	3.3

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