Operating Information by Segment and Geographic Area - External Revenue and Segment Profit (Loss) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
External revenue
Revenues	$ 3,937,707	$ 3,842,235	$ 10,622,201	$ 11,268,305
Segment Profit (Loss)
Segment Profit (Loss)	57,800	173,100	(536,700)	277,000
Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	57,800	173,100	(536,700)	277,000
Energy & Chemicals
External revenue
Revenues	1,611,600	1,902,300	4,485,200	5,859,800
Energy & Chemicals | Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	84,900	50,200	(124,900)	253,000
Mining & Industrial
External revenue
Revenues	1,374,000	973,300	3,703,600	2,377,400
Mining & Industrial | Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	56,900	20,900	129,100	56,900
Infrastructure & Power
External revenue
Revenues	392,500	412,300	951,800	1,250,600
Infrastructure & Power | Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	1,000	102,300	(193,300)	(13,200)
Diversified Services
External revenue
Revenues	521,700	526,300	1,525,000	1,706,900
Diversified Services | Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	10,800	22,600	22,400	51,500
Diversified Services | Intercompany
External revenue
Revenues	81,000	73,000	253,000	257,000
Other
External revenue
Revenues	37,900	28,000	(43,400)	73,600
Other | Reportable segments
Segment Profit (Loss)
Segment Profit (Loss)	$ (95,800)	(22,900)	(370,000)	$ (71,200)
Forecast revisions for estimated cost growth for a fixed-price, gas-fired power plant project | Mining & Industrial | Reportable segments
Segment reporting information
Change in Forecast Estimate, Increase (Decrease) in Project Cost		$ 125,000	$ 135,000
Change In Forecast Estimate Increase Decrease In Project Cost Per Diluted Share		$ 0.68	$ 0.96