Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 938	$ 927	$ 667
Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	308	346
Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	630	581
Operating Segments | Government Solutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	565	600
Operating Segments | Government Solutions | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	184	266
Operating Segments | Government Solutions | Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	381	334
Operating Segments | Technology Solutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	62	73
Operating Segments | Technology Solutions | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	6	11
Operating Segments | Technology Solutions | Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	56	62
Operating Segments | Energy Solutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	310	254
Operating Segments | Energy Solutions | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	118	69
Operating Segments | Energy Solutions | Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	192	185
Subtotal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	937	927
Subtotal | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	308	346
Subtotal | Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	629	581
Non-strategic Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	1	0
Non-strategic Business | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	0	0
Non-strategic Business | Trade & Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 1	$ 0