Qualified Defined Benefit Pension Plans and Retiree Medical and Life Insurance Plans by Asset Category (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		$ 33,909	$ 36,605
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	2,658	2,968
U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	4,790	6,431
International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	6,121	5,566
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	1,935	6,078
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	3,929	4,242
U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	5,069	4,579
U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	1,377	613
Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	3,252	1,807
Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		3,131	2,952
Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		1,108	762
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		522	570
Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	(26)	2
Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		33,866	36,570
Receivables, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		43	35
Fair value, inputs, level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	2,658	2,968
Fair value, inputs, level 1 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	4,771	6,363
Fair value, inputs, level 1 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	6,087	5,525
Fair value, inputs, level 1 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	614	2,047
Fair value, inputs, level 1 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]		39
Fair value, inputs, level 1 | Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	1	2
Fair value, inputs, level 1 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		14,131	16,944
Fair value, inputs, level 2 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	19	67
Fair value, inputs, level 2 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	24	31
Fair value, inputs, level 2 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	1,321	4,031
Fair value, inputs, level 2 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	3,914	4,201
Fair value, inputs, level 2 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	5,069	4,579
Fair value, inputs, level 2 | U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	1,377	613
Fair value, inputs, level 2 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	3,246	1,759
Fair value, inputs, level 2 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		92	33
Fair value, inputs, level 2 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		167	66
Fair value, inputs, level 2 | Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	(27)
Fair value, inputs, level 2 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		15,202	15,380
Fair value, inputs, level 3 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]		1
Fair value, inputs, level 3 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	10	10
Fair value, inputs, level 3 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	15	41
Fair value, inputs, level 3 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	[1]	6	9
Fair value, inputs, level 3 | Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		3,131	2,952
Fair value, inputs, level 3 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		1,016	729
Fair value, inputs, level 3 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		355	504
Fair value, inputs, level 3 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		$ 4,533	$ 4,246

[1] Cash and cash equivalents, equity securities, fixed income securities and commodities included derivative assets and liabilities whose fair values were not material as of December 31, 2015 and 2014. LMIMCO's investment policies restrict the use of derivatives to either establish long exposures for purposes of expediency or capital efficiency or to hedge risks to the extent of a plan's current exposure to such risks. Most derivative transactions are settled on a daily basis.