Qualified Defined Benefit Pension Plans And Retiree Medical And Life Insurance Plans By Asset Category (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 32,888		$ 29,041
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Cash and cash equivalents	3,563		2,886
U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,931	[1]	3,878	[1]
International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,389	[1]	3,776	[1]
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,825	[1]	2,143	[1]
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,106	[1]	1,044	[1]
U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	12,013	[1]	10,040	[1]
Other fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	484	[1]	553	[1]
Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,461		2,286
Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	529		278
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	806		825
Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	736	[1]	1,269	[1]
Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	32,843		28,978
Receivables, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	45		63
Fair value, inputs, level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Cash and cash equivalents	3,563		2,886
Fair value, inputs, level 1 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,871	[1]	3,834	[1]
Fair value, inputs, level 1 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,363	[1]	3,750	[1]
Fair value, inputs, level 1 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	980	[1]	1,016	[1]
Fair value, inputs, level 1 | Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	735	[1]	992	[1]
Fair value, inputs, level 1 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	12,512		12,478
Fair value, inputs, level 2 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	50	[1]	37	[1]
Fair value, inputs, level 2 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	15	[1]	11	[1]
Fair value, inputs, level 2 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,845	[1]	1,127	[1]
Fair value, inputs, level 2 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,045	[1]	946	[1]
Fair value, inputs, level 2 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	12,013	[1]	10,040	[1]
Fair value, inputs, level 2 | Other fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	435	[1]	508	[1]
Fair value, inputs, level 2 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	25
Fair value, inputs, level 2 | Commodities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1	[1]	277	[1]
Fair value, inputs, level 2 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	16,429		12,946
Fair value, inputs, level 3 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	10	[1]	7	[1]
Fair value, inputs, level 3 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	11	[1]	15	[1]
Fair value, inputs, level 3 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	61	[1]	98	[1]
Fair value, inputs, level 3 | Other fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	49	[1]	45	[1]
Fair value, inputs, level 3 | Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,461		2,286
Fair value, inputs, level 3 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	504		278
Fair value, inputs, level 3 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	806		825
Fair value, inputs, level 3 | Total excluding receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 3,902		$ 3,554

[1] Equity securities, fixed income securities, and commodities included derivative assets and liabilities whose fair values were not material as of December 31, 2012 and 2011. 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.