Basis Of Presentation and Significant Accounting Policies Restatement (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	$ 3,335.1	$ 3,143.8	$ 9,682.3	$ 9,229.9
Costs and Expenses	3,221.0	2,863.7	9,119.8	8,527.2
Net income (loss) attributable to TechnipFMC plc	$ (119.1)	$ 136.9	$ (1.2)	$ 337.7
Basic (usd per share)	$ (0.27)	$ 0.30		$ 0.73
Diluted (usd per share)	$ (0.27)	$ 0.30	$ 0	$ 0.73
Basic (in shares)	446.9	454.5	448.6	460.0
Diluted (in shares)	446.9	459.0	448.6	464.0
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		$ 3,143.8		$ 9,229.9
Costs and Expenses		2,863.7		8,527.2
Net income (loss) attributable to TechnipFMC plc		$ 136.9		$ 337.7
Basic (usd per share)		$ 0.30		$ 0.73
Diluted (usd per share)		$ 0.30		$ 0.73
Basic (in shares)		454.5		460.0
Diluted (in shares)		459.0		464.0
Services
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue	$ 2,409.6	$ 2,276.9	$ 7,009.5	$ 6,616.9
Cost of goods and services sold	1,926.0	1,860.2	5,520.1	5,488.4
Services | Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		2,487.9		7,159.2
Cost of goods and services sold		2,046.6		5,846.0
Services | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		(211.0)		(542.3)
Cost of goods and services sold		(186.4)		(357.6)
Products
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue	839.8	806.2	2,471.9	2,449.6
Cost of goods and services sold	$ 743.9	667.4	$ 2,237.2	1,917.5
Products | Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		595.2		1,907.3
Cost of goods and services sold		481.0		1,559.9
Products | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		211.0		542.3
Cost of goods and services sold		$ 186.4		$ 357.6