Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
FAS/CAS pension adjustment	$ 876	$ 902	$ 400
Qualified Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	820	827	836
Interest cost	1,809	1,861	1,791
Expected return on plan assets	(2,408)	(2,666)	(2,734)
Recognized net actuarial losses	1,506	1,359	1,599
Amortization of net prior service (credit) cost	(355)	(362)	(365)
Total net periodic benefit cost	1,372	1,019	1,127
Total net periodic benefit cost	1,372	1,019	1,127
Qualified Defined Benefit Pension Plans | Discontinued Operations | Information Systems & Global Solutions
Defined Benefit Plan Disclosure [Line Items]
Net prior service (credit) and cost - Recognition of Previously Deferred Amounts		14	24
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	20	24	21
Interest cost	102	119	110
Expected return on plan assets	(128)	(138)	(147)
Recognized net actuarial losses	19	34	43
Amortization of net prior service (credit) cost	15	22	4
Total net periodic benefit cost	28	61	31
Total net periodic benefit cost	$ 28	$ 61	$ 31