Quarterly Financial Data (Unaudited) - Summary of Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 3,157,000	$ 3,103,000	$ 3,236,000	$ 2,939,000	$ 3,268,000	$ 3,457,000	$ 3,735,000	$ 3,698,000	$ 12,434,879	$ 14,157,929	$ 15,454,484
Cost of revenue	(3,003,000)	(2,997,000)	(3,177,000)	(2,846,000)	(3,144,000)	(3,324,000)	(3,656,000)	(3,634,000)	(12,023,284)	(13,758,403)	(15,660,536)
Earnings (loss) from Cont Ops before taxes	(157,000)	70,000	(13,000)	(28,000)	(42,000)	54,000	23,000	(32,000)	(127,705)	3,494	(839,465)
Net earnings (loss) from Cont Ops	(145,000)	43,000	(14,000)	(28,000)	(61,000)	26,000	(8,000)	31,000	(144,194)	(12,362)	(1,321,430)
Net earnings (loss) from Cont Ops attributable to Fluor
Net earnings (loss) from Cont Ops	(161,000)	46,000	(6,000)	(61,000)	(107,000)	21,000	(15,000)	22,000	(181,736)	(79,079)	(1,282,642)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(118,000)	(6,000)	(108,000)	(26,000)	(56,000)	(2,000)	(10,000)	(288,000)	(258,434)	(355,967)	(239,522)
Net earnings	$ (279,000)	$ 40,000	$ (114,000)	$ (87,000)	$ (163,000)	$ 19,000	$ (25,000)	$ (266,000)	$ (440,170)	$ (435,046)	$ (1,522,164)
Basic EPS available to Fluor common stockholders:
Net earnings (loss) from continuing operations (in dollars per share)	$ (1.21)	$ 0.26	$ (0.08)	$ (0.43)	$ (0.76)	$ 0.15	$ (0.11)	$ 0.15	$ (1.46)	$ (0.56)	$ (9.16)
Net earnings from discontinued operations (in dollars per share)	(0.84)	(0.04)	(0.76)	(0.19)	(0.40)	(0.01)	(0.07)	(2.05)	(1.83)	(2.53)	(1.71)
Net earnings (loss) (in dollars per share)	(2.04)	0.22	(0.84)	(0.62)	(1.16)	0.14	(0.18)	(1.90)
Diluted earnings (loss) per share attributable to Fluor Corporation:
Net earnings (loss) from continuing operations (in dollars per share)	(1.21)	0.26	(0.08)	(0.43)	(0.76)	0.15	(0.11)	0.15	(1.46)	(0.56)	(9.16)
Net earnings from discontinued operations (in dollars per share)	(0.84)	(0.04)	(0.76)	(0.19)	(0.40)	(0.01)	(0.07)	(2.05)	$ (1.83)	$ (2.53)	$ (1.71)
Net earnings (loss) (in dollars per share)	$ (2.04)	$ 0.22	$ (0.84)	$ (0.62)	$ (1.16)	$ 0.14	$ (0.18)	$ (1.90)