Postretirement Benefit Plans - Amounts Recognized in Other Comprehensive Income (Loss) Related to Postretirement Benefit Plans, Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and losses - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	$ (416)	$ (1,161)	$ (1,204)
Actuarial gains and losses - Recognition of Previously Deferred Amounts	1,455	1,030	938
Net prior service credit and cost - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(85)	(219)	(28)
Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(501)	(1,380)	(1,232)
Net prior service credit and cost - Recognition of Previously Deferred Amounts	(253)	(228)	(230)
Recognition of Previously Deferred Amounts	1,202	802	708
Reclassifications from divestiture of IS&GS business	0	0	(134)
Discontinued Operations | Information Systems & Global Solutions
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net prior service credit and cost - Recognition of Previously Deferred Amounts			(9)
Reclassifications from divestiture of IS&GS business			134
Qualified Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and losses - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(570)	(1,172)	(1,236)
Actuarial gains and losses - Recognition of Previously Deferred Amounts	1,396	974	879
Net prior service credit and cost - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(6)	(219)	(54)
Net prior service credit and cost - Recognition of Previously Deferred Amounts	(255)	(229)	(235)
Retiree Medical and Life Insurance Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and losses - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	71	77	94
Actuarial gains and losses - Recognition of Previously Deferred Amounts	4	12	22
Net prior service credit and cost - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(79)	0	27
Net prior service credit and cost - Recognition of Previously Deferred Amounts	12	10	14
Other plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and losses - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	83	(66)	(62)
Actuarial gains and losses - Recognition of Previously Deferred Amounts	55	44	37
Net prior service credit and cost - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	0	0	(1)
Net prior service credit and cost - Recognition of Previously Deferred Amounts	$ (10)	$ (9)	$ (9)