Quarterly Financial Information (Unaudited) (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
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,197.3	$ 1,014.3	$ 1,206.1	$ 1,192.1	$ 1,099.4	$ 923.6	$ 1,154.4	$ 1,107.9	$ 4,609.8	$ 4,285.3	$ 2,531.2
Gross margin	556.0	432.4	550.5	544.7	491.7	395.2	490.4	502.5	2,083.6	1,879.8	951.8
Income (loss) from continuing operations before equity in (earnings) loss of affiliates, non-operating pension and postretirement charges (income), interest expense, net and income taxes	112.1	159.9	267.8	281.8	177.5	105.1	133.3	325.0	821.6	740.9	158.5
Income (loss) from continuing operations	30.7	110.8	194.4	207.6	156.7	50.9	99.8	230.2	543.5	537.6	(133.1)
Discontinued operations, net of income taxes	(33.5)	(21.3)	(18.1)	9.6	(122.1)	23.9	32.7	39.4	(63.3)	(26.1)	671.5
Net income (loss)	(2.8)	89.5	176.3	217.2	34.6	74.8	132.5	269.6	480.2	511.5	538.4
Less: Net income (loss) attributable to noncontrolling interests	0.4	(0.9)	1.8	1.5	2.2	2.0	2.8	2.4	2.8	9.4	2.6
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
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
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):
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
Diluted (in shares)	130,900	131,600	132,300	133,200	135,100	136,400	136,200	136,200	132,002	135,879	134,255
Environmental Exit Cost [Line Items]
Charges to expense for new losses									$ 138.8	$ 178.2	$ 105.6
Pending Litigation | Middleport Litigation
Environmental Exit Cost [Line Items]
Charges to expense for new losses					$ 106.3