Basis Of Presentation and Significant Accounting Policies Restatement (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	$ 3,434.2	$ 2,960.9	$ 6,347.2	$ 6,086.1
Costs and Expenses	3,120.6	2,777.6	5,898.8	5,663.5
Net income attributable to TechnipFMC plc	$ 97.0	$ 105.7	$ 117.9	$ 200.8
Basic (usd per share)	$ 0.22	$ 0.23	$ 0.26	$ 0.43
Diluted (usd per share)	$ 0.21	$ 0.23	$ 0.26	$ 0.43
Basic (in shares)	447.5	461.4	447.7	462.8
Diluted (in shares)	451.2	463.3	451.9	464.2
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		$ 2,960.9		$ 6,086.1
Costs and Expenses		2,777.6		5,663.5
Net income attributable to TechnipFMC plc		$ 105.7		$ 200.8
Basic (usd per share)		$ 0.23		$ 0.43
Diluted (usd per share)		$ 0.23		$ 0.43
Basic (in shares)		461.4		462.8
Diluted (in shares)		463.3		464.2
Services
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue	$ 2,548.8	$ 2,066.0	$ 4,599.9	$ 4,340.0
Cost of goods and services sold	1,949.9	1,801.3	3,594.1	3,628.2
Services | Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		2,243.9		4,671.3
Cost of goods and services sold		1,846.9		3,799.4
Services | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		(177.9)		(331.3)
Cost of goods and services sold		(45.6)		(171.2)
Products
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue	832.8	841.6	1,632.1	1,643.4
Cost of goods and services sold	$ 771.6	589.7	$ 1,493.3	1,250.1
Products | Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		663.7		1,312.1
Cost of goods and services sold		544.1		1,078.9
Products | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		177.9		331.3
Cost of goods and services sold		$ 45.6		$ 171.2