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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly results of operations
Revenue	$ 4,801,000	$ 4,658,000	$ 4,883,800	$ 4,823,800	$ 5,027,400	$ 4,941,600	$ 4,716,100	$ 4,835,900	$ 19,166,599	$ 19,520,970	$ 19,036,525
Cost of revenue	4,624,900	4,432,200	4,673,600	4,766,000	4,812,400	4,720,100	4,684,100	4,685,900	18,496,675	18,902,480	18,246,209
Earnings (loss) before taxes	160,800	146,500	183,600	(9,100)	151,500	165,400	(23,900)	93,400	481,752	386,441	546,600
Net earnings (loss)	77,900	96,000	131,200	(12,100)	80,800	112,900	(6,600)	77,400	$ 292,958	$ 264,469	$ 327,449
Net earnings (loss) attributable to Fluor Corporation	$ 50,300	$ 77,300	$ 114,800	$ (17,600)	$ 60,300	$ 94,500	$ (24,000)	$ 60,600
Earnings (loss) per share
Basic (in dollars per share)	$ 0.36	$ 0.55	$ 0.82	$ (0.13)	$ 0.43	$ 0.68	$ (0.17)	$ 0.43	$ 1.60	$ 1.37	$ 2.02
Diluted (in dollars per share)	$ 0.36	$ 0.55	$ 0.81	$ (0.13)	$ 0.43	$ 0.67	$ (0.17)	$ 0.43	$ 1.59	$ 1.36	$ 2.00