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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net loss attributable to TechnipFMC plc	$ (3.9)	$ (119.1)	$ (3,248.3)	$ (1.2)
Weighted average number of shares outstanding (in shares)	449,400	446,900	448,400	448,600
Total shares and dilutive securities (in shares)	449,400	446,900	448,400	448,600
Basic earnings per share attributable to TechnipFMC plc (usd per share)	$ (0.01)	$ (0.27)	$ (7.24)
Diluted earnings per share attributable to technipFMC plc (usd per share)	$ (0.01)	$ (0.27)	$ (7.24)	$ 0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	13,700	4,900	8,500	3,900
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	4,300	4,700	3,500
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,500	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	4,500	600	2,000	300
Retained Earnings
Antidilutive Securities Excluded from Computation of Earnings Per Share
Net loss attributable to TechnipFMC plc	$ (3.9)	$ (119.1)	$ (3,248.3)	$ (1.2)
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	600	5,100	3,600	4,900