STOCKHOLDERS’ EQUITY - Accumulated other comprehensive loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 3,418.4	$ 4,214.3
Other comprehensive income (loss), net of tax	120.1	(36.9)
Ending balance	3,490.4	3,695.5
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,158.4)
Other comprehensive income (loss) before reclassifications, net of tax	125.3
Reclassification adjustment for net losses included in net income (loss), net of tax	0.0
Other comprehensive income (loss), net of tax	125.3
Ending balance	(1,033.1)
Hedging
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(17.3)
Other comprehensive income (loss) before reclassifications, net of tax	(14.9)
Reclassification adjustment for net losses included in net income (loss), net of tax	6.4
Other comprehensive income (loss), net of tax	(8.5)
Ending balance	(25.8)
Defined Pension  and Other Post-Retirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(129.3)
Other comprehensive income (loss) before reclassifications, net of tax	(0.2)
Reclassification adjustment for net losses included in net income (loss), net of tax	3.1
Other comprehensive income (loss), net of tax	2.9
Ending balance	(126.4)
Accumulated Other Comprehensive  Loss Attributable to TechnipFMC plc
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,305.0)	(1,622.5)
Other comprehensive income (loss) before reclassifications, net of tax	110.2
Reclassification adjustment for net losses included in net income (loss), net of tax	9.5
Other comprehensive income (loss), net of tax	119.7	(37.0)
Ending balance	(1,185.3)	$ (1,400.8)
Accumulated Other Comprehensive  Loss Attributable to Non-Controlling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5.7)
Other comprehensive income (loss) before reclassifications, net of tax	0.4
Reclassification adjustment for net losses included in net income (loss), net of tax	0.0
Other comprehensive income (loss), net of tax	0.4
Ending balance	$ (5.3)