Operating Information by Segment and Geographic Area - Total Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Segment reporting information
Total assets	$ 7,292,469	$ 7,966,658
Other
Segment reporting information
Total assets	43,400	68,500
Corporate
Segment reporting information
Total assets	3,232,700	3,379,300
Reportable segments | Energy & Chemicals
Segment reporting information
Total assets	1,006,800	1,139,300
Reportable segments | Mining & Industrial
Segment reporting information
Total assets	624,100	594,900
Reportable segments | Infrastructure & Power
Segment reporting information
Total assets	505,000	471,200
Reportable segments | Government
Segment reporting information
Total assets	623,800	629,100
Reportable segments | Diversified Services
Segment reporting information
Total assets	$ 1,004,000	$ 1,290,600