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Operations by Business Segment and Geographic Area - Additional Operating Information (Details 5) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment reporting information
Revenue	$ 4,370,700	$ 4,384,600	$ 4,810,100	$ 4,548,600	$ 5,455,200	$ 5,440,100	$ 5,251,700	$ 5,384,600	$ 18,114,048	$ 21,531,577	$ 27,351,573
Government Segment
Segment reporting information
Revenue									2,557,400	2,511,900	2,749,100
Global Services Segment
Segment reporting information
Revenue									499,100	581,200	605,800
Power Segment
Segment reporting information
Revenue									946,700	1,004,100	1,389,200
Power Segment \| Forecast revisions for gas-fired power plant in Brunswick County, Virginia
Segment reporting information
Loss									60,000
Reportable segments \| Government Segment \| Favorable resolution of various issues with U.S. government related to 2001-2013
Segment reporting information
Income recognized											57,000
Reportable segments \| Government Segment \| Resolution of U.S. government challenges as to reimbursability of certain costs
Segment reporting information
Income recognized											31,000
Reportable segments \| Government Segment \| Favorable court ruling that resolved certain U.S. government disputed items
Segment reporting information
Income recognized											11,000
Reportable segments \| Government Segment \| Closeout and final disposition of other U.S. government matters
Segment reporting information
Income recognized											15,000
Reportable segments \| Power Segment \| Nu Scale Power
Segment reporting information
Research and development expense									80,000	46,000	53,000
Reportable segments \| Power Segment \| Nu Scale Power \| Cost-sharing agreement, research and development activities \| U.S. Department of Energy \| Total cost of revenue
Segment reporting information
Qualified expenses reimbursed									65,000	38,000
Intercompany \| Global Services Segment
Segment reporting information
Revenue									$ 439,000	$ 531,000	$ 505,000