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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income attributable to TechnipFMC plc	$ 136.9	$ 121.0	$ 337.7	$ 267.2
Weighted average number of shares outstanding (in shares)	454.5	467.2	460.0	466.8
Total shares and dilutive securities (in shares)	459.0	469.7	464.0	468.3
Basic earnings per share attributable to TechnipFMC plc (usd per share)	$ 0.30	$ 0.26	$ 0.73	$ 0.57
Diluted earnings per share attributable to technipFMC plc (usd per share)	$ 0.30	$ 0.26	$ 0.73	$ 0.57
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	1.2	0.7	1.0	0.1
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	0.1		0.1	0.1
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	3.2	1.8	2.9	1.3