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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 3,655,700	$ 3,803,200	$ 4,091,000	$ 4,118,600	$ 4,408,700	$ 4,628,600	$ 4,146,400	$ 4,133,600	$ 15,668,477	$ 17,317,284	$ 18,851,008
Cost of revenue	3,533,000	3,669,500	4,023,500	4,057,200	4,348,000	4,537,300	4,577,600	4,070,900	15,283,226	17,533,864	18,281,628
Earnings (loss) from Cont Ops before taxes	(41,700)	52,200	10,900	(228,400)	(271,800)	(258,800)	(511,900)	(29,000)	(207,052)	(1,071,495)	385,749
Net earnings (loss) from Cont Ops	(67,200)	23,400	(20,200)	(161,600)	(322,300)	(754,100)	(436,100)	(44,200)	(225,644)	(1,556,725)	212,418
Amounts attributable to Fluor Corporation:
Net earnings (loss) from Cont Ops	(115,000)	19,100	(26,900)	(171,100)	(293,700)	(766,600)	(397,400)	(68,100)	(293,899)	(1,525,767)	153,033
Net earnings (loss) attributable to Fluor Corporation from Disc Ops	(48,300)	200	1,900	(94,900)	(2,500)	23,500	(16,600)	(800)	(141,147)	3,603	20,435
NET EARNINGS (LOSS) ATTRIBUTABLE TO FLUOR CORPORATION	$ (163,300)	$ 19,300	$ (25,000)	$ (266,000)	$ (296,200)	$ (743,100)	$ (414,000)	$ (68,900)	$ (435,046)	$ (1,522,164)	$ 173,468
Basic earnings (loss) per share attributable to Fluor Corporation:
Net earnings (loss) from continuing operations (in dollars per share)	$ (0.82)	$ 0.14	$ (0.19)	$ (1.22)	$ (2.10)	$ (5.47)	$ (2.84)	$ (0.49)	$ (2.09)	$ (10.89)	$ 1.09
Net earnings from discontinued operations (in dollars per share)	(0.34)	0	0.01	(0.68)	(0.01)	0.17	(0.11)	0	(1.01)	0.02	0.15
Net earnings (loss) (in dollars per share)	(1.16)	0.14	(0.18)	(1.90)	(2.11)	(5.30)	(2.95)	(0.49)	(3.10)	(10.87)	1.24
Diluted earnings (loss) per share attributable to Fluor Corporation:
Net earnings (loss) from continuing operations (in dollars per share)	(0.82)	0.14	(0.19)	(1.22)	(2.10)	(5.47)	(2.84)	(0.49)	(2.09)	(10.89)	1.08
Net earnings from discontinued operations (in dollars per share)	(0.34)	0	0.01	(0.68)	(0.01)	0.17	(0.11)	0	(1.01)	0.02	0.15
Net earnings (loss) (in dollars per share)	$ (1.16)	$ 0.14	$ (0.18)	$ (1.90)	$ (2.11)	$ (5.30)	$ (2.95)	$ (0.49)	$ (3.10)	$ (10.87)	$ 1.23

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227