Percentage-of-Completion Contracts (Details) - USD ($) $ in Millions		3 Months Ended			12 Months Ended
	May 26, 2016	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2014
Billed and Unbilled Contract Claims Subject to Uncertainty [Line Items]
Contract Settlement, Amount	$ 150
Proceeds from Contract Settlements		$ 16	$ 72	$ 62
Contracts Receivable, Claims and Uncertain Amounts							$ 0
Billings in Excess of Cost					$ 56		45
IRAQ
Billed and Unbilled Contract Claims Subject to Uncertainty [Line Items]
Loss on Contracts					$ 0	$ 153
Total Estimated Loss on Contracts						532	532
Accounts Receivable, Unapproved Contract Claims						116	25
Deductions (Charges)						28	$ 16
Unapproved Change Orders, Amount						$ 32
Costs in Excess of Billings, Current								$ 6