Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Amounts Attributable to Parent, Disclosures [Abstract]
Net earnings (loss) from Cont Ops attributable to Fluor	$ 46,730	$ 21,518	$ (20,911)	$ 28,206
Less: Dividends on CPS	9,750	0	14,625	0
Net earnings (loss) from Cont Ops available to Fluor common stockholders	36,980	21,518	(35,536)	28,206
Net earnings (loss) from Disc Ops attributable to Fluor	(6,261)	(2,177)	(140,090)	(299,814)
Net earnings (loss) available to Fluor common stockholders	$ 30,719	$ 19,341	$ (175,626)	$ (271,608)
Weighted average common shares outstanding (shares)	141,412	140,598	141,229	140,465
Diluted effect:
CPS (in shares)	0	0	0	0
Stock options, RSU's, restricted stock and performance-based award units (in shares)	0	570	0	464
Weighted average diluted shares outstanding (in shares)	141,412	141,168	141,229	140,929
Basic EPS available to Fluor common stockholders:
Net earnings (loss) from Cont Ops (in dollars per share)	$ 0.26	$ 0.15	$ (0.25)	$ 0.20
Net earnings (loss) from Disc Ops (in dollars per share)	(0.04)	(0.01)	(0.99)	(2.13)
Diluted EPS available to Fluor common stockholders:
Net earnings (loss) from Cont Ops (in dollars per share)	0.26	0.15	(0.25)	0.20
Net earnings (loss) from Disc Ops (in dollars per share)	$ (0.04)	$ (0.01)	$ (0.99)	$ (2.13)