Contingencies and Commitments - Narrative (Details) $ in Millions			1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 23, 2019 AUD ($)	Dec. 13, 2016 AUD ($)	Sep. 30, 2018 action	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Aug. 31, 2019 USD ($)	Aug. 23, 2019 USD ($)	Aug. 12, 2016 USD ($)
Loss Contingencies [Line Items]
Number of actions filed | action			9
Contracts receivable				$ 209,000,000	$ 198,000,000
Amount of disputed back charges				$ 2,000,000	$ 2,000,000
Pending Litigation
Loss Contingencies [Line Items]
Damages sought		$ 1,470
Sadara Chemical Company | Pending Litigation
Loss Contingencies [Line Items]
Damages sought	$ 100
Estimate of possible loss							$ 574,000,000
Fluor/TECHINT | Pending Litigation
Loss Contingencies [Line Items]
Estimate of possible loss								$ 250,000,000
Purple Line Transit Project | Minimum
Loss Contingencies [Line Items]
Right to terminate contract period				365 days
DB Contract | Minimum
Loss Contingencies [Line Items]
Right to terminate contract period				365 days
Barrick | Fluor/TECHINT
Loss Contingencies [Line Items]
Letters of credit outstanding, amount						$ 35,000,000
Parent Company | Barrick | Fluor/TECHINT
Loss Contingencies [Line Items]
Letters of credit outstanding, amount						23,500,000
Partnership Interest | Barrick | Fluor/TECHINT
Loss Contingencies [Line Items]
Letters of credit outstanding, amount						$ 11,500,000
Purple Line Transit Partners, LLC
Loss Contingencies [Line Items]
Partnership ownership interest				15.00%
Purple Line Transit Constructors, LLC
Loss Contingencies [Line Items]
Partnership ownership interest				50.00%