NEW ACCOUNTING PRONOUNCEMENTS - Revenue Standard Impact on Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets
Accounts receivable, net	$ 2,574.3	$ 2,571.4
Inventories	1,541.8	1,446.5
Total current assets	4,596.8	4,594.3
Other assets	492.4	477.4
Total assets	20,184.3	19,963.5
Current liabilities
Other current liabilities	1,068.9	1,000.7
Total current liabilities	3,982.8	3,475.2
Deferred income taxes	652.8	635.4
Total liabilities	12,514.4	12,309.7
Equity
Retained earnings	8,097.0	8,011.6
Accumulated other comprehensive loss	(1,558.3)	(1,643.4)
Total Ecolab shareholders' equity	7,601.0	7,583.6
Total equity	7,669.9	7,653.8	$ 6,941.0	$ 6,980.4
Total liabilities and equity	$ 20,184.3	19,963.5
Previously Reported
Current assets
Accounts receivable, net		2,574.1
Inventories		1,445.9
Total current assets		4,596.4
Other assets		474.2
Total assets		19,962.4
Current liabilities
Other current liabilities		957.3
Total current liabilities		3,431.8
Deferred income taxes		642.8
Total liabilities		12,273.7
Equity
Retained earnings		8,045.4
Accumulated other comprehensive loss		(1,642.3)
Total Ecolab shareholders' equity		7,618.5
Total equity		7,688.7
Total liabilities and equity		19,962.4
Adjustment | Revenue Standard Adoption
Current assets
Accounts receivable, net		(2.7)
Inventories		0.6
Total current assets		(2.1)
Other assets		3.2
Total assets		1.1
Current liabilities
Other current liabilities		43.4
Total current liabilities		43.4
Deferred income taxes		(7.4)
Total liabilities		36.0
Equity
Retained earnings		(33.8)
Accumulated other comprehensive loss		(1.1)
Total Ecolab shareholders' equity		(34.9)
Total equity		(34.9)
Total liabilities and equity		$ 1.1