EARNINGS (LOSS) PER SHARE (Reconciliation Of Number Of Shares Used For Basic And Diluted Earnings Per Share ("EPS") Calculation ) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share
Income (loss) from continuing operations attributable to TechnipFMC plc	$ (174.7)	$ (177.6)	$ 255.6	$ (3,412.4)
Income (loss) from discontinued operations attributable to TechnipFMC plc	7.7	189.3	(54.4)	168.0
Net income (loss) attributable to TechnipFMC plc	$ (167.0)	$ 11.7	$ 201.2	$ (3,244.4)
Weighted average number of shares outstanding (in shares)	450,600	448,300	450,400	447,900
Total shares and dilutive securities (in shares)	450,600	448,300	454,900	447,900
Earnings (loss) per share from continuing operations basic (usd per share)	$ (0.39)	$ (0.40)	$ 0.57	$ (7.62)
Earnings (loss) per share from continued operations diluted (usd per share)	(0.39)	(0.40)	0.56	(7.62)
Earnings (loss) per share from discontinued operations basic (usd per share)	(0.02)	(0.42)	0.12	(0.38)
Earnings (loss) per share from discontinued operations diluted (usd per share)	(0.02)	(0.42)	0.12	(0.38)
Basic (usd per share)	(0.37)	0.03	0.45	(7.24)
Diluted (usd per share)	$ (0.37)	$ 0.03	$ 0.44	$ (7.24)
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,100	15,800	1,600	8,600
Share option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,600	4,700	1,600	4,700
Restricted share units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	6,300	0	1,800
Performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	500	4,800	0	2,100
Share option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	5,300	1,200		3,400
Restricted share units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	0	0	3,800	0
Performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)			700