Acquisitions, Goodwill and Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	$ 2,441	$ 2,354
Accumulated Amortization		(1,739)	(1,676)
Net Carrying Amount		702	678
Contract and Program Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1],[2]	1,684	1,633
Accumulated Amortization	[2]	(1,320)	(1,281)
Net Carrying Amount		364	352
Tradenames and Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	465	446
Accumulated Amortization		(160)	(139)
Net Carrying Amount		305	307
Technology and Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	137	121
Accumulated Amortization		(105)	(102)
Net Carrying Amount		32	19
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	155	154
Accumulated Amortization		(154)	(154)
Net Carrying Amount		$ 1	$ 0

[1] Change in gross carrying amounts consists primarily of adjustments for acquired intangible assets and foreign currency translation.

[2] Consists of acquired backlog and probable follow-on work and associated customer relationships