Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Antidilutive shares excluded from diluted EPS (in shares)									300	200	1,500
Earnings (loss) attributable to FMC stockholders:
Continuing operations, net of income taxes	$ 30.3	$ 111.7	$ 192.6	$ 206.1	$ 157.7	$ 48.9	$ 97.0	$ 227.8	$ 540.7	$ 531.4	$ (135.7)
Discontinued operations, net of income taxes	(33.5)	(21.3)	(18.1)	9.6	(125.3)	23.9	32.7	39.4	(63.3)	(29.3)	671.5
Net income (loss) attributable to FMC stockholders	$ (3.2)	$ 90.4	$ 174.5	$ 215.7	$ 32.4	$ 72.8	$ 129.7	$ 267.2	477.4	502.1	535.8
Less: Distributed and undistributed earnings allocable to restricted award holders									(1.5)	(2.4)	0.0
Net income (loss) allocable to common stockholders									$ 475.9	$ 499.7	$ 535.8
Basic earnings (loss) per common share attributable to FMC stockholders:
Continuing operations (in dollars per share)	$ 0.23	$ 0.85	$ 1.46	$ 1.56	$ 1.17	$ 0.36	$ 0.72	$ 1.69	$ 4.12	$ 3.94	$ (1.01)
Discontinued operations (in dollars per share)	(0.25)	(0.16)	(0.14)	0.07	(0.93)	0.18	0.24	0.29	(0.48)	(0.22)	5.00
Net income (loss) attributable to FMC stockholders (in dollars per share)	(0.02)	0.69	1.32	1.63	0.24	0.54	0.96	1.98	3.64	3.72	3.99
Diluted earnings (loss) per common share attributable to FMC stockholders:
Continuing operations (in dollars per share)	0.23	0.85	1.46	1.55	1.17	0.36	0.72	1.67	4.10	3.91	(1.01)
Discontinued operations (in dollars per share)	(0.25)	(0.16)	(0.14)	0.07	(0.93)	0.18	0.24	0.29	(0.48)	(0.22)	5.00
Net income (loss) attributable to FMC stockholders (in dollars per share)	$ (0.02)	$ 0.69	$ 1.32	$ 1.62	$ 0.24	$ 0.54	$ 0.96	$ 1.96	$ 3.62	$ 3.69	$ 3.99
Shares (in thousands):
Weighted average number of shares of common stock outstanding - Basic (in shares)	129,700	130,400	131,100	131,900	133,700	134,900	134,800	134,600	130,761	134,406	134,255
Weighted average additional shares assuming conversion of potential common shares (in shares)									1,241	1,473	0
Shares – diluted basis (in shares)	130,900	131,600	132,300	133,200	135,100	136,400	136,200	136,200	132,002	135,879	134,255