Retirement Benefits (Details 11) (Level 3 significant unobservable inputs, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	$ 5,338	$ 4,952
Actual return on plan assets:
Unrealized gains (losses), net	(26)	172
Realized gains (losses), net	42	8
Purchases	1,105	1,386
Sales	(1,431)	(1,180)
Ending Balance	5,028	5,338
Asset Backed
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	4	4
Actual return on plan assets:
Unrealized gains (losses), net	0	0
Realized gains (losses), net	0	0
Purchases	0	0
Sales	0	0
Ending Balance	4	4
High yield debt
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	41	78
Actual return on plan assets:
Unrealized gains (losses), net	10	(2)
Realized gains (losses), net	0	0
Purchases	0	10
Sales	(23)	(45)
Ending Balance	28	41
Hedge funds
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	1,405	1,521
Actual return on plan assets:
Unrealized gains (losses), net	13	(43)
Realized gains (losses), net	47	25
Purchases	0	413
Sales	(707)	(511)
Ending Balance	758	1,405
Private equities
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	2,098	1,945
Actual return on plan assets:
Unrealized gains (losses), net	(122)	19
Realized gains (losses), net	0	(13)
Purchases	259	503
Sales	(255)	(356)
Ending Balance	1,980	2,098
Real Estate
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	1,788	1,402
Actual return on plan assets:
Unrealized gains (losses), net	68	198
Realized gains (losses), net	0	(4)
Purchases	846	460
Sales	(446)	(268)
Ending Balance	2,256	1,788
Domestic equities
Changes in Fair Value of Plan Assets, Significant Unobservable Inputs (Table Amounts) [Abstract]
Beginning Balance	2	2
Actual return on plan assets:
Unrealized gains (losses), net	5	0
Realized gains (losses), net	(5)	0
Purchases	0	0
Sales	0	0
Ending Balance	$ 2	$ 2