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 Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share
Income (loss) from continuing operations attributable to TechnipFMC plc	$ 430.3	$ (3,234.8)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(62.1)	(21.3)
Net Income (loss) attributable to TechnipFMC plc	$ 368.2	$ (3,256.1)
Weighted average number of shares outstanding (in shares)	449.7	447.5
Total shares and dilutive securities (in shares)	451.1	447.5
Earnings (loss) per share from continuing operations basic (usd per share)	$ 0.96	$ (7.23)
Earnings (loss) per share from continued operations diluted (usd per share)	0.95	(7.23)
Earnings (loss) per share from discontinued operations basic (usd per share)	(0.14)	(0.05)
Earnings (loss) per share from discontinued operations diluted (usd per share)	(0.14)	(0.05)
Earnings (loss) attributable to TechnipFMC plc, Basic (usd per share)	0.82	(7.28)
Earnings (loss) attributable to TechnipFMC plc, Diluted (usd per share)	$ 0.81	$ (7.28)
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	6.6	8.3
Share option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1.7	4.7
Restricted share units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	4.9	1.1
Performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0.0	2.5
Share option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)		2.7
Restricted share units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	1.4	0.0