Acquisitions and Dispositions (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Customer relationships	Sep. 30, 2012 Patents	Sep. 30, 2012 Trademarks	Sep. 30, 2012 Other technology	Dec. 31, 2011 Nalco merger Initial Valuation	Dec. 31, 2011 Nalco merger Initial Valuation Customer relationships	Dec. 31, 2011 Nalco merger Initial Valuation Patents	Dec. 31, 2011 Nalco merger Initial Valuation Trade names	Dec. 31, 2011 Nalco merger Initial Valuation Trademarks	Dec. 31, 2011 Nalco merger Initial Valuation Other technology	Sep. 30, 2012 Nalco merger 2012 Adjustments to Fair Value	Sep. 30, 2012 Nalco merger Actual Valuation	Sep. 30, 2012 Nalco merger Actual Valuation Customer relationships	Sep. 30, 2012 Nalco merger Actual Valuation Patents	Sep. 30, 2012 Nalco merger Actual Valuation Trade names	Sep. 30, 2012 Nalco merger Actual Valuation Trademarks	Sep. 30, 2012 Nalco merger Actual Valuation Other technology
ACQUISITIONS AND DISPOSITIONS
Net adjustment made to the preliminary purchase price allocation														$ 52.5
Assets acquired and liabilities assumed
Current assets								1,869.6						(0.1)	1,869.5
Property, plant and equipment								1,069.2						(1.2)	1,068.0
Other assets								97.3						(3.3)	94.0
Identifiable intangible assets									2,160.0	321.0	1,230.0	79.0	91.0			2,160.0	321.0	1,230.0	79.0	91.0
Total assets acquired								6,917.1						(4.6)	6,912.5
Current liabilities								1,105.5						19.7	1,125.2
Long-term debt								2,858.4							2,858.4
Pension and postretirement benefits								505.7						5.7	511.4
Net deferred tax liability								1,188.7						(8.6)	1,180.1
Noncontrolling interests and other liabilities								167.7						31.1	198.8
Total liabilities and noncontrolling interests assumed								5,826.0						47.9	5,873.9
Goodwill								4,403.9						54.6	4,458.5
Total consideration transferred								5,495.0						2.1	5,497.1
Estimated time period after merger date to finalize the purchase price allocation, maximum		1 year
Weighted average useful lives of identifiable intangible assets acquired		13 years	14 years	15 years	14 years	15 years	8 years
Pro forma net sales and results of operations
Net sales	2,967.3		8,419.6
Net income attributable to Ecolab	$ 189.2		$ 548.5
Earnings attributable to Ecolab per common share
Basic (in dollars per share)	$ 0.63		$ 1.82
Diluted (in dollars per share)	$ 0.61		$ 1.78