Equity - Rollforward of Stockholders Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 2,707.1
Net income (loss) attributable to FMC stockholders	267.2	$ (124.2)
Net income (loss) attributable to noncontrolling interests	2.4	0.4
Net income (loss)	269.6	(123.8)
Stock compensation plans	10.2
Net pension and other benefit actuarial gains (losses) and prior service costs, net of income tax	3.6	$ 9.3
Net hedging gains (losses) and other, net of income tax	1.9
Foreign currency translation adjustments	49.7
Dividends ($0.165 per share)	(22.3)
Repurchases of common stock	(5.1)
Ending balance	$ 3,014.7
Dividends paid (in USD per share)	$ 0.165
FMC Stockholders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 2,681.8
Net income (loss) attributable to FMC stockholders	267.2
Stock compensation plans	10.2
Net pension and other benefit actuarial gains (losses) and prior service costs, net of income tax	3.6
Net hedging gains (losses) and other, net of income tax	1.9
Foreign currency translation adjustments	49.3
Dividends ($0.165 per share)	(22.3)
Repurchases of common stock	(5.1)
Ending balance	2,986.6
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	25.3
Net income (loss) attributable to noncontrolling interests	2.4
Stock compensation plans	0.0
Net pension and other benefit actuarial gains (losses) and prior service costs, net of income tax	0.0
Net hedging gains (losses) and other, net of income tax	0.0
Foreign currency translation adjustments	0.4
Dividends ($0.165 per share)	0.0
Repurchases of common stock	0.0
Ending balance	$ 28.1