Recast 2017 and 2016 Financial Information (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income (Loss) Attributable to Parent	$ 356	$ 1,244	$ 789	$ 840	$ 672	$ 750	$ 677	$ 770	$ 3,229	$ 2,869	$ 2,043
Adjustments to reconcile to net cash provided by operating activities:
Depreciation and amortization									800	475	456
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit									(655)	536	(950)
Deferred income taxes									234	985	(60)
Changes in assets and liabilities:
Stock-based compensation									86	94	93
Increase (Decrease) in Accounts Receivable									(202)	209	(46)
Unbilled receivables, net									(297)	(422)	(211)
Inventoried costs, net									37	(25)	53
Prepaid expenses and other assets									(56)	(92)	(117)
Accounts payable and other liabilities									381	570	18
Retiree benefits									(1,083)	(946)	(375)
Other, net									29	43	125
Income taxes payable, net									(258)	(157)	148
Net cash provided by operating activities									3,827	2,613	2,813
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income (Loss) Attributable to Parent										2,015	2,200
Adjustments to reconcile to net cash provided by operating activities:
Depreciation and amortization										475	456
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit										0	0
Deferred income taxes										603	36
Changes in assets and liabilities:
Stock-based compensation										94	93
Increase (Decrease) in Accounts Receivable										187	(55)
Unbilled receivables, net										490	516
Inventoried costs, net										(36)	15
Prepaid expenses and other assets										(81)	(110)
Accounts payable and other liabilities										539	198
Retiree benefits										(191)	393
Other, net										43	125
Income taxes payable, net										(157)	148
Net cash provided by operating activities										2,613	2,813
Adjustments for change to Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Period Benefit (Cost) [Member] | Adjustments for Change in Accounting Principle [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income (Loss) Attributable to Parent	$ (394)	$ 100	$ 100	$ 101	$ 525	$ 107	$ 122	$ 120	(93)	874	(113)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation and amortization									0	0	0
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit									(655)	536	(950)
Deferred income taxes									(29)	417	(69)
Changes in assets and liabilities:
Stock-based compensation									0	0	0
Increase (Decrease) in Accounts Receivable									0	0	0
Unbilled receivables, net									0	0	0
Inventoried costs, net									0	0	0
Prepaid expenses and other assets									0	0	0
Accounts payable and other liabilities									0	0	0
Retiree benefits									(533)	(755)	(768)
Other, net									0	0	0
Income taxes payable, net									0	0	0
Net cash provided by operating activities									$ 0	0	0
Accounting Standards Update 2014-09 [Member] | Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income (Loss) Attributable to Parent										(20)	(44)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation and amortization										0	0
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit										0	0
Deferred income taxes										(35)	(27)
Changes in assets and liabilities:
Stock-based compensation										0	0
Increase (Decrease) in Accounts Receivable										22	9
Unbilled receivables, net										(68)	(305)
Inventoried costs, net										11	38
Prepaid expenses and other assets										(11)	(7)
Accounts payable and other liabilities										31	(180)
Retiree benefits										0	0
Other, net										0	0
Income taxes payable, net										0	0
Net cash provided by operating activities										0	0
Accounting Standards Update 2017-07 [Domain] | Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income (Loss) Attributable to Parent										0	0
Adjustments to reconcile to net cash provided by operating activities:
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit										$ 0	$ 0