Contracts in Process (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Contracts Receivable [Abstract]
Unbilled contract receivables, gross		$ 1,874	$ 1,890
Unliquidated progress payments		(761)	(827)
Unbilled contract receivables, net		1,113	1,063
Inventoried contract costs, gross		891	998
Unliquidated progress payments		(71)	(203)
Inventoried contract costs, net		820	795
Total contracts in process		$ 1,933	1,858
Percentage of unbilled contract receivables, net billed and collected within one year		92.00%
Contracts Receivable [Line Items]
Percentage of incurred costs billed		80.00%
Summary of Inventory for Long Term Contracts or Programs [Roll Forward]
Amounts included in inventoried contract costs at beginning of the year		$ 173	137	$ 114
Contract costs incurred [Abstract]:
IRAD and B&P		333	304	280
Other G&A	[1]	842	749	742
Total		1,175	1,053	1,022
Amounts charged to cost of sales		(1,179)	(1,017)	(999)
Amounts included in inventoried contract costs at end of the year		169	173	137
Severance and restructuring cost		91	13	14
Operating Expenses [Abstract]
Selling, general and administrative expenses		278	223	261
Research and development expenses		63	54	52
Total		$ 341	$ 277	$ 313
Maximum [Member]
Contracts Receivable [Line Items]
Number of years for billed and collected, unbilled contract receivables		1 year

[1] Amounts include severance and restructuring-related costs of $91 million, $13 million and $14 million for the years ended December 31, 2017, 2016 and 2015, respectively.