Earnings 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, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income (loss) attributable to TechnipFMC plc	$ 95.1	$ (18.7)
Weighted average number of shares outstanding (in shares)	464.3	466.6
Total shares and dilutive securities (in shares)	465.7	466.6
Basic earnings per share attributable to TechnipFMC plc (usd per share)	$ 0.20	$ (0.04)
Diluted earnings per share attributable to technipFMC plc (usd per share)	$ 0.20	$ (0.04)
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	0.1
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	1.3