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Commitments and Contingencies (Details) - USD ($) $ in Millions					1 Months Ended	3 Months Ended
	May 24, 2018	Jul. 21, 2017	Jul. 03, 2017	Apr. 01, 2017	Dec. 31, 2014	Dec. 31, 2018	Sep. 02, 2016
Advatech LLC
Commitments and Contingencies
Percentage of ownership in joint venture						60.00%
Advatech LLC | Genco
Commitments and Contingencies
Damages claimed, value		$ 81.0
Invoice amount							$ 81.0
DOE Deactivation, Demolition, And Removal Project | Department of Energy | Maximum
Commitments and Contingencies
Cost-reimbursement at risk						$ 106.0
DOE Deactivation, Demolition, And Removal Project | WGI Ohio and DOE | Minimum
Commitments and Contingencies
Cost-reimbursement at risk						106.0
DOE Deactivation, Demolition, And Removal Project | WGI Ohio and DOE | Maximum
Commitments and Contingencies
Cost-reimbursement at risk						146.0
DOE Deactivation, Demolition, And Removal Project | WGI Ohio
Commitments and Contingencies
Claim to DOE, including additional fees					$ 103.0
Possible costs which may exceed contracted amounts					$ 100.0
DOE Deactivation, Demolition, And Removal Project | WGI Ohio | Minimum
Commitments and Contingencies
Cost-reimbursement at risk						146.0
AECOM-Canyon Equity Fund, L.P
Commitments and Contingencies
Capital commitments						$ 35.0
Term of capital commitments						10 years
URS | Design build contractor
Commitments and Contingencies
Damages claimed, value	$ 11.9		$ 70.0	$ 8.2
Standby letter of credit
Commitments and Contingencies
Contingency liability						$ 537.0
Surety Bond
Commitments and Contingencies
Surety bonds issued						$ 5,600.0

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