Other Comprehensive Income (Loss) - Changes in AOCI Balances by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	$ 1,694	$ 1,771	$ 1,567	$ 1,263
Total OCI, net of tax	(23)	(23)	(12)	(23)
Balance, end of year	1,923	1,844	1,923	1,844
Attributable to Fluor:
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(355)	(417)	(366)	(417)
OCI before reclassifications	(23)	(22)	(19)	(16)
Amounts reclassified from AOCI	0	(3)	7	(9)
Total OCI, net of tax	(23)	(25)	(12)	(25)
Balance, end of year	(378)	(442)	(378)	(442)
Foreign Currency Translation
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(304)	(259)	(299)	(261)
OCI before reclassifications	(32)	(21)	(37)	(19)
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	(32)	(21)	(37)	(19)
Balance, end of year	(336)	(280)	(336)	(280)
Ownership Share of Equity Method Investees’ OCI
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(38)	(56)	(56)	(54)
OCI before reclassifications	14	(3)	24	(5)
Amounts reclassified from AOCI	0	0	8	0
Total OCI, net of tax	14	(3)	32	(5)
Balance, end of year	(24)	(59)	(24)	(59)
DB Plans
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(17)	(116)	(18)	(119)
OCI before reclassifications	0	0	1	0
Amounts reclassified from AOCI	0	1	0	4
Total OCI, net of tax	0	1	1	4
Balance, end of year	(17)	(115)	(17)	(115)
Unrealized Gain (Loss) on Hedges
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	4	14	7	17
OCI before reclassifications	(5)	2	(7)	8
Amounts reclassified from AOCI	0	(4)	(1)	(13)
Total OCI, net of tax	(5)	(2)	(8)	(5)
Balance, end of year	(1)	12	(1)	12
Attributable to NCI:
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(2)	(5)	(3)	(4)
OCI before reclassifications	0	3	1	2
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	0	3	1	2
Balance, end of year	(2)	(2)	(2)	(2)
Foreign Currency Translation
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	(2)	(5)	(3)	(4)
OCI before reclassifications	0	3	1	2
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	0	3	1	2
Balance, end of year	(2)	(2)	(2)	(2)
Ownership Share of Equity Method Investees’ OCI
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	0	0	0	0
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	0	0	0	0
Balance, end of year	0	0	0	0
DB Plans
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	0	0	0	0
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	0	0	0	0
Balance, end of year	0	0	0	0
Unrealized Gain (Loss) on Hedges
Changes in AOCI balances by component (after-tax)
Balance, beginning of year	0	0	0	0
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	0	0	0	0
Total OCI, net of tax	0	0	0	0
Balance, end of year	$ 0	$ 0	$ 0	$ 0