Contract Assets and Contract Liabilities (Contract Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Disaggregation of Revenue [Line Items]
Contract liability	$ 484	$ 463	$ 377
Operating Segments | Government Solutions
Disaggregation of Revenue [Line Items]
Contract liability	261	261
Operating Segments | Technology Solutions
Disaggregation of Revenue [Line Items]
Contract liability	73	98
Operating Segments | Energy Solutions
Disaggregation of Revenue [Line Items]
Contract liability	147	100
Subtotal
Disaggregation of Revenue [Line Items]
Contract liability	481	459
Non-strategic Business
Disaggregation of Revenue [Line Items]
Contract liability	$ 3	$ 4