Discontinued Operations - Earnings From Discontinued Operations (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	May 31, 2021	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
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net earnings (loss) from Disc Ops										$ (257,552)	$ (354,429)	$ (231,692)
Net earnings (loss) from Disc Ops attributable to Fluor		$ (118,000)	$ (6,000)	$ (108,000)	$ (26,000)	$ (56,000)	$ (2,000)	$ (10,000)	$ (288,000)	(258,434)	(355,967)	(239,522)
Disc Ops
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue										1,721,968	1,726,232	2,123,076
Cost of revenue										(1,693,381)	(1,722,596)	(2,127,896)
Gross profit										28,587	3,636	(4,820)
G&A										(4,351)	(234)	(239)
Impairment, restructuring and other exit costs										(246,285)	(342,933)	(214,158)
Loss on sale of AMECO										(26,670)	(1,390)	0
Foreign currency gain (loss)										(385)	(2,023)	(1,678)
Operating profit (loss)										(249,104)	(342,944)	(220,895)
Interest (expense) income, net										(4,968)	(4,792)	(7,024)
Earnings (loss) before taxes from Disc Ops										(254,072)	(347,736)	(227,919)
Income tax (expense) benefit										(3,480)	(6,693)	(3,774)
Net earnings (loss) from Disc Ops										(257,552)	(354,429)	(231,693)
Less: Net earnings (loss) from Disc Ops attributable to NCI										882	1,538	7,829
Net earnings (loss) from Disc Ops attributable to Fluor										(258,434)	(355,967)	(239,522)
Disc Ops | Stork Holding B.V.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue										1,599,705	1,509,238	1,805,705
Cost of revenue										(1,559,327)	(1,514,374)	(1,794,266)
Gross profit										40,378	(5,136)	11,439
G&A										(4,351)	0	0
Impairment, restructuring and other exit costs										(193,200)	(196,503)	(92,906)
Loss on sale of AMECO										0	0	0
Foreign currency gain (loss)										(228)	(2,078)	(413)
Operating profit (loss)										(157,401)	(203,717)	(81,880)
Interest (expense) income, net										(4,995)	(4,633)	(7,365)
Earnings (loss) before taxes from Disc Ops										(162,396)	(208,350)	(89,245)
Income tax (expense) benefit										(3,480)	(2,736)	(3,265)
Net earnings (loss) from Disc Ops										(165,876)	(211,086)	(92,510)
Less: Net earnings (loss) from Disc Ops attributable to NCI										883	1,537	7,169
Net earnings (loss) from Disc Ops attributable to Fluor										(166,759)	(212,623)	(99,679)
Disc Ops | AMECO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue										122,263	216,994	317,371
Cost of revenue										(124,948)	(195,024)	(354,782)
Gross profit										(2,685)	21,970	(37,411)
G&A										0	(234)	(239)
Impairment, restructuring and other exit costs										(53,085)	(146,430)	(121,252)
Loss on sale of AMECO	$ (27,000)									(26,670)	(1,390)	0
Foreign currency gain (loss)										(157)	55	(1,265)
Operating profit (loss)										(82,597)	(126,029)	(160,167)
Interest (expense) income, net										27	(159)	341
Earnings (loss) before taxes from Disc Ops										(82,570)	(126,188)	(159,826)
Income tax (expense) benefit										0	(3,957)	3,938
Net earnings (loss) from Disc Ops										(82,570)	(130,145)	(155,888)
Less: Net earnings (loss) from Disc Ops attributable to NCI										(1)	1	660
Net earnings (loss) from Disc Ops attributable to Fluor										(82,569)	(130,146)	(156,548)
Disc Ops | Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue										0	0	0
Cost of revenue										(9,106)	(13,198)	21,152
Gross profit										(9,106)	(13,198)	21,152
G&A										0	0	0
Impairment, restructuring and other exit costs										0	0	0
Loss on sale of AMECO										0	0	0
Foreign currency gain (loss)										0	0	0
Operating profit (loss)										(9,106)	(13,198)	21,152
Interest (expense) income, net										0	0	0
Earnings (loss) before taxes from Disc Ops										(9,106)	(13,198)	21,152
Income tax (expense) benefit										0	0	(4,447)
Net earnings (loss) from Disc Ops										(9,106)	(13,198)	16,705
Less: Net earnings (loss) from Disc Ops attributable to NCI										0	0	0
Net earnings (loss) from Disc Ops attributable to Fluor										$ (9,106)	$ (13,198)	$ 16,705