Retirement Benefits (Details 9) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	$ 26,279	$ 25,273
Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	1,775	1,499
Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	4,878	4,452
International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	4,737	4,214
U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	957	1,602
U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	909	974
Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	440	422
Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	5,710	4,744
Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	608	549
High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	586	923
Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	228	185
Hedge funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	632	821
Private equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2,030	2,075
Real estate
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2,759	2,767
Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	30	46
Level 1
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	7,474	6,694
Level 1 | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	38	32
Level 1 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	4,729	4,163
Level 1 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2,675	2,473
Level 1 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	32	26
Level 2
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	13,378	12,909
Level 2 | Cash & cash equivalents
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	1,737	1,467
Level 2 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	147	287
Level 2 | International equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2,062	1,741
Level 2 | U.S. Treasuries
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	957	1,602
Level 2 | U.S. Government Agency
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	909	974
Level 2 | Non-U.S. Government
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	440	422
Level 2 | Corporate debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	5,710	4,744
Level 2 | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	604	545
Level 2 | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	586	922
Level 2 | Bank loans
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	228	185
Level 2 | Other
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	(2)	20
Level 3
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	5,427	5,670	5,028
Level 3 | Domestic equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2	2
Level 3 | Asset backed
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	4	4
Level 3 | High yield debt
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	0	1
Level 3 | Hedge funds
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	632	821
Level 3 | Private equities
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	2,030	2,075	1,980
Level 3 | Real estate
Plan Assets by Fair Value Measurement Input (Table Amounts) [Abstract]
Fair value of plan assets at end of year	$ 2,759	$ 2,767	$ 2,256