Contingencies and Commitments (Details) $ in Millions			1 Months Ended					3 Months Ended
	Aug. 23, 2019 USD ($)	Dec. 13, 2016 AUD ($) claim	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) wall	Mar. 31, 2023 referee	Oct. 31, 2022 USD ($)	Sep. 30, 2018 action	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Aug. 31, 2019 USD ($)	Aug. 12, 2016 USD ($)
Loss Contingencies [Line Items]
Number of derivative actions filed | action							11
Fluor T E C H I N T | Barrick
Loss Contingencies [Line Items]
Letters of credit outstanding, amount										$ 36,000,000
Fluor T E C H I N T | Barrick | Parent Company
Loss Contingencies [Line Items]
Letters of credit outstanding, amount										24,000,000
Fluor T E C H I N T | Barrick | Partnership Interest
Loss Contingencies [Line Items]
Letters of credit outstanding, amount										$ 12,000,000
SEC Investigation
Loss Contingencies [Line Items]
De-recognized pre-petition accounts receivable				$ 15,000,000
Pending litigation | Santos Ltd
Loss Contingencies [Line Items]
Damages sought		$ 1,470
Number of referees appointed | referee					3
Estimate of possible loss		$ 236
Pending litigation | Santos Ltd Claim 1
Loss Contingencies [Line Items]
Number of pending matters | claim		1
Loss contingency, panel referred damages awarded from other party, value		$ 700
Pending litigation | Santos Ltd Claim 2
Loss Contingencies [Line Items]
Loss contingency, panel referred damages awarded from other party, value		$ 790
Pending litigation | North Texas Tollway Authority
Loss Contingencies [Line Items]
Damages sought				$ 227,000,000		$ 100,000,000
Number of retaining walls | wall				65
Pending litigation | Sadara Chemical Company
Loss Contingencies [Line Items]
Damages sought	$ 100,000,000
Estimate of possible loss	$ 574,000,000
Litigation settlement, expense									$ 14,000,000
Pending litigation | Sadara Chemical Company | Minimum
Loss Contingencies [Line Items]
Litigation settlement interest			$ 3,000,000
Pending litigation | Sadara Chemical Company | Maximum
Loss Contingencies [Line Items]
Litigation settlement interest			5,000,000
Pending litigation | Fluor T E C H I N T
Loss Contingencies [Line Items]
Estimate of possible loss			$ 364,000,000					$ 364,000,000			$ 250,000,000
Pending litigation | Fluor T E C H I N T | Barrick
Loss Contingencies [Line Items]
Litigation settlement, expense									$ 12,000,000
Litigation settlement interest								$ 11,000,000