Retirement Benefits (Details 10) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	$ 24,024		$ 22,286
Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	0		14
Fixed income securities | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,840	[1]	1,603	[1]
Fixed income securities | U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,780		1,872
Fixed income securities | U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	968		965
Fixed income securities | Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	401		324
Fixed income securities | Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	4,123		3,686
Fixed income securities | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	532		529
Fixed income securities | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,167		1,018
Fixed income securities | Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	223		150
Alternative Investments | Hedge funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	758		1,405
Alternative Investments | Private equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,980		2,098
Alternative Investments | Real estate
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	2,256		1,788
Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	3,977		3,852
International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	4,019		2,982
Level 1
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	5,444		5,190
Level 1 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	(5)
Level 1 | Fixed income securities | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	92	[1]	75	[1]
Level 1 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	3,657		3,849
Level 1 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,700		1,266
Level 2
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	13,552		11,758
Level 2 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	5		14
Level 2 | Fixed income securities | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,748	[1]	1,528	[1]
Level 2 | Fixed income securities | U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,780		1,872
Level 2 | Fixed income securities | U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	968		965
Level 2 | Fixed income securities | Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	401		324
Level 2 | Fixed income securities | Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	4,123		3,686
Level 2 | Fixed income securities | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	528		525
Level 2 | Fixed income securities | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,139		977
Level 2 | Fixed income securities | Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	223		150
Level 2 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	318		1
Level 2 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	2,319		1,716
Level 3
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	5,028		5,338
Level 3 | Fixed income securities | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	4		4
Level 3 | Fixed income securities | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	28		41
Level 3 | Alternative Investments | Hedge funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	758		1,405
Level 3 | Alternative Investments | Private equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	1,980		2,098
Level 3 | Alternative Investments | Real estate
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	2,256		1,788
Level 3 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at the end of the year	$ 2		$ 2

[1] Cash and cash equivalents are predominantly held in money market funds.