Business Combination Transactions (Narrative) (Details) $ in Millions				3 Months Ended		11 Months Ended	12 Months Ended
		Apr. 18, 2018 USD ($)	Jan. 16, 2017 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 18, 2018	Jan. 29, 2018 Rate	Jan. 29, 2018
Business Acquisition [Line Items]
Other Asset Impairment Charges							$ 495.4	$ 372.9
Goodwill, Purchase Accounting Adjustments							9.9	19.7
Goodwill, Acquired During Period								85.0	$ 5,165.9
Merger transaction and integration costs (Note 2)							31.2	36.5	101.8
Technip Odebrecht PLSV CV
Business Acquisition [Line Items]
Acquired assets							391.0
Vessels acquired							335.2
Liability assumed							239.9
Short-term and current portion of long-term debt							203.1
Business Combination, Separately Recognized Transactions, Net Gains and Losses							(0.9)
Other Asset Impairment Charges							84.2
Business Combination, Bargain Purchase, Gain Recognized, Amount							$ 83.3
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								62.5
Technip Offshore Finland Oy [Member]
Business Acquisition [Line Items]
Divestitures, Percentage of Voting Interest Sold										100.00%
Gain (Loss) on Disposition of Stock in Subsidiary				$ 27.8
FMC Technologies
Business Acquisition [Line Items]
Percentage of business acquired			100.00%
Goodwill, Purchase Accounting Adjustments					$ 19.7
FMCTI Merger
Business Acquisition [Line Items]
Acquired assets			$ 6,763.7
Vessels acquired			1,293.3
Liability assumed			3,773.7
Short-term and current portion of long-term debt			$ 319.5
FMC Technologies, Inc. exchange ratio	[1]		0.5
Revenues contributed						$ 3,441.1
Net income (loss) contributed						$ 251.2
Business Combination, Consideration Transferred			$ 8,170.7
Technip
Business Acquisition [Line Items]
FMC Technologies, Inc. exchange ratio			2.0
FMC Technologies
Business Acquisition [Line Items]
FMC Technologies, Inc. exchange ratio			1.0
Noncontrolling Interest | Island Offshore Subsea AS
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners											51.00%	51.00%
Payments to Acquire Businesses, Gross		$ 42.4
Goodwill, Acquired During Period		$ 85.0
Subsea
Business Acquisition [Line Items]
Goodwill, Acquired During Period								$ 85.0	$ 2,532.6
Technip Odebrecht PLSV CV | Subsea
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage							50.00%

[1] As the calculation is deemed to reflect a share capital increase of the accounting acquirer, the FMC Technologies exchange ratio (1 share of TechnipFMC for 1 share of FMC Technologies as provided in the business combination agreement) is adjusted by dividing the FMC Technologies exchange ratio by the Technip exchange ratio (2 shares of TechnipFMC for 1 share of Technip as provided in the business combination agreement), i.e.,  1 ⁄ 2 = 0.5 in order to reflect the number of shares of Technip that FMC Technologies stockholders would have received if Technip was to have issued its own shares.