CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 3,635,600	$ 3,910,425	$ 3,424,488	$ 3,377,504	$ 3,946,466	$ 3,841,219	$ 3,939,278	$ 3,445,492					$ 14,348,018	$ 15,172,454	$ 14,806,511
Cost of revenue	3,690,700	3,843,794	3,884,363	3,356,464	3,823,228	3,653,355	3,843,301	3,483,349					14,775,399	14,803,234	14,528,782
Other (income) and expenses
Corporate general and administrative expense		10,347	48,681	56,383	4,237	42,418	12,734	59,041					159,089	118,428	183,697
Impairment, restructuring and other exit costs	145,000	333,988	26,671	27,368	0	0	0	0					532,600	0	0
Loss on pension settlement													137,898	21,900	184
Interest expense		18,984	18,876	18,629	19,013	24,238	16,783	17,111					74,104	77,144	67,458
Interest income		(13,965)	(14,009)	(12,722)	(11,476)	(9,504)	(7,925)	(7,347)					(54,372)	(36,252)	(27,419)
Total cost and expenses		4,193,148	3,964,582	3,446,122	3,836,368	3,729,148	3,866,786	3,552,154					15,624,718	14,984,454	14,752,702
Earnings (loss) from continuing operations before taxes	(385,300)	(282,723)	(540,094)	(68,618)	110,098	112,071	72,492	(106,662)					(1,276,700)	188,000	53,809
Income tax expense (benefit)		489,736	(82,234)	6,270	106,194	27,448	17,530	(18,922)					440,982	132,250	16,356
Net earnings (loss) from continuing operations	(412,500)	(772,459)	(457,860)	(74,888)	3,904	84,623	54,962	(87,740)					(1,717,682)	55,750	37,453
Net earnings from discontinued operations		41,806	5,161	29,843	63,184	13,245	33,692	66,984					164,558	177,103	189,311
Net earnings (loss)		(730,653)	(452,699)	(45,045)	67,088	97,868	88,654	(20,756)	$ (497,744)	$ 67,899	$ (1,228,397)	$ 165,767	(1,553,124)	232,853	226,764
Less: Net earnings (loss) attributable to NCI from continuing operations		10,260	(40,966)	20,529	15,027	19,297	9,065	3,167					(41,450)	46,556	64,533
Net earnings (loss) attributable to Fluor Corporation from continuing operations	(381,300)	(782,719)	(416,894)	(95,417)	(11,123)	65,326	45,897	(90,907)					(1,676,232)	9,194	(27,080)
Less: Net earnings attributable to NCI from discontinued operations		2,185	2,288	3,330	3,817	4,481	2,169	2,362					10,490	12,829	8,560
Net earnings attributable to Fluor Corporation from discontinued operations	85,100	39,621	2,873	26,513	59,367	8,764	31,523	64,622					154,068	164,274	180,751
Net earnings (loss) attributable to Fluor Corporation	(296,200)	(743,098)	(414,021)	(68,904)	48,244	74,090	77,420	(26,285)					(1,522,164)	173,468	153,671
Amounts attributable to Fluor Corporation
Net earnings (loss) from continuing operations	(381,300)	(782,719)	(416,894)	(95,417)	(11,123)	65,326	45,897	(90,907)					(1,676,232)	9,194	(27,080)
Net earnings from discontinued operations	85,100	39,621	2,873	26,513	59,367	8,764	31,523	64,622					154,068	164,274	180,751
Net earnings (loss) attributable to Fluor Corporation	$ (296,200)	$ (743,098)	$ (414,021)	$ (68,904)	$ 48,244	$ 74,090	$ 77,420	$ (26,285)					$ (1,522,164)	$ 173,468	$ 153,671
Basic earnings (loss) per share attributable to Fluor Corporation
Net earnings (loss) from continuing operations (in dollars per share)	$ (2.72)	$ (5.58)	$ (2.97)	$ (0.68)	$ (0.08)	$ 0.46	$ 0.33	$ (0.65)					$ (11.97)	$ 0.07	$ (0.19)
Net earnings from discontinued operations (in dollars per share)	0.61	0.28	0.02	0.19	0.42	0.07	0.22	0.46					1.10	1.17	1.29
Net earnings (loss) (in dollars per share)	(2.11)	(5.30)	(2.95)	(0.49)	0.34	0.53	0.55	(0.19)					(10.87)	1.24	1.10
Diluted earnings (loss) per share attributable to Fluor Corporation
Net earnings (loss) from continuing operations (in dollars per share)	(2.72)	(5.58)	(2.97)	(0.68)	(0.08)	0.46	0.33	(0.65)					(11.97)	0.07	(0.19)
Net earnings from discontinued operations (in dollars per share)	0.61	0.28	0.02	0.19	0.42	0.06	0.22	0.46					1.10	1.16	1.28
Net earnings (loss) (in dollars per share)	$ (2.11)	$ (5.30)	$ (2.95)	$ (0.49)	$ 0.34	$ 0.52	$ 0.55	$ (0.19)					$ (10.87)	$ 1.23	$ 1.09