Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Lease and other revenue										$ 222.7	$ 194.6	$ 0.0
Total revenue		$ 3,323.0	$ 3,143.8	$ 2,960.9	$ 3,125.2	$ 3,683.0	$ 4,140.9	$ 3,845.0	$ 3,388.0	12,552.9	15,056.9	9,199.6
Costs and expenses
Cost of lease and other revenue										143.4	137.2	0.0
Selling, general and administrative expense										1,140.6	1,060.9	572.6
Research and development expense										189.2	212.9	105.4
Impairment, restructuring and other expense (Note 17)										1,831.2	191.5	343.0
Merger transaction and integration costs (Note 2)										36.5	101.8	92.6
Total costs and expenses										13,470.5	14,091.7	8,743.6
Other income (expense), net										(323.9)	(25.9)	6.5
Income from equity affiliates (Note 9)										114.3	55.6	117.7
Income before interest income, interest expense and income taxes										(1,127.2)	994.9	580.2
Interest income										121.4	140.8	85.3
Interest expense										(482.3)	(456.0)	(114.1)
Income (loss) before income taxes	[1]									(1,488.1)	679.7	551.4
Provision for income taxes (Note 19)										422.7	545.5	180.3
Net income (loss)		(2,246.5)	134.2	110.1	91.4	(127.5)	117.9	159.0	(15.2)	(1,910.8)	134.2	371.1
Net (income) loss attributable to noncontrolling interests										(10.8)	(20.9)	22.2
Net income (loss) attributable to TechnipFMC plc		$ (2,259.3)	$ 136.9	$ 105.7	$ 95.1	$ (153.9)	$ 121.0	$ 164.9	$ (18.7)	$ (1,921.6)	$ 113.3	$ 393.3
Earnings (loss) per share attributable to TechnipFMC plc (Note 6)
Basic earnings (loss) per share (usd per share)		$ (5.00)	$ 0.30	$ 0.23	$ 0.20	$ (0.33)	$ 0.26	$ 0.35	$ (0.04)	$ (4.20)	$ 0.24	$ 3.29
Diluted earnings (loss) per share (usd per share)		$ (5.00)	$ 0.30	$ 0.23	$ 0.20	$ (0.33)	$ 0.26	$ 0.35	$ (0.04)	$ (4.20)	$ 0.24	$ 3.16
Weighted average shares outstanding (Note 6)
Basic (in shares)										458.0	466.7	119.4
Diluted (in shares)										458.0	468.3	125.1
Service [Member]
Revenue
Revenue										$ 9,765.0	$ 12,210.5	$ 9,128.7
Costs and expenses
Cost of product revenue										7,895.1	9,984.0	7,585.7
Product [Member]
Revenue
Revenue										2,565.2	2,651.8	70.9
Costs and expenses
Cost of product revenue										$ 2,234.5	$ 2,403.4	$ 44.3

[1] Includes amounts attributable to noncontrolling interests.