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 Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income (loss) attributable to TechnipFMC plc	$ 11.7	$ 97.0	$ (3,244.4)	$ 117.9
Weighted average number of shares outstanding (in shares)	448,300	447,500	447,900	447,700
Total shares and dilutive securities (in shares)	449,500	451,200	447,900	451,900
Basic earnings per share attributable to TechnipFMC plc (usd per share)	$ 0.03	$ 0.22	$ (7.24)	$ 0.26
Diluted earnings per share attributable to technipFMC plc (usd per share)	$ 0.03	$ 0.21	$ (7.24)	$ 0.26
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	15,800	5,000	8,600	4,800
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,700	4,900	4,700	4,600
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6,300	0	1,800	100
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,800	100	2,100	100
Retained Earnings
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net income (loss) attributable to TechnipFMC plc	$ 11.7	$ 97.0	$ (3,244.4)	$ 117.9
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	300	1,600		1,800
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Dilutive effect of share-based payment arrangements (in shares)	900	2,100		2,400
Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			3,400