Pension Plans, Retirement Benefits and Savings Plans (details) - Change in Projected Benefit Obligation and Change in Plan Assets (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change in projected benefit obligation [Roll Forward]
Plan amendments	$ (31)
Pension Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	2,889	2,572
Benefits earned	113	98
Interest cost on benefit obligation, change in projected benefit obligation	138	135
Actuarial loss (gain)	242	214
Benefits paid	(125)	(130)
Foreign currency exchange rate change, change in projected benefit obligation	4
Benefit obligation, balance, end of year	3,261	2,889
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	2,500	2,425
Actual return on plan assets	252	8
Company contributions	228	197
Benefits paid	(125)	(130)
Foreign currency exchange rate change, change in plan assets	4
Fair value of plan assets, balance, end of year	2,859	2,500
Funded status of plan at end of year	(402)	(389)
Qualified Domestic Pension Plan [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	2,706	2,399
Benefits earned	107	93
Interest cost on benefit obligation, change in projected benefit obligation	129	125
Actuarial loss (gain)	225	207
Benefits paid	(112)	(118)
Benefit obligation, balance, end of year	3,055	2,706	2,399
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	2,414	2,342
Actual return on plan assets	242	5
Company contributions	217	185	35
Benefits paid	(112)	(118)
Fair value of plan assets, balance, end of year	2,761	2,414	2,342
Funded status of plan at end of year	(294)	(292)
Nonqualified and Foreign Pension Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	183	173
Benefits earned	6	5
Interest cost on benefit obligation, change in projected benefit obligation	9	10
Actuarial loss (gain)	17	7
Benefits paid	(13)	(12)
Foreign currency exchange rate change, change in projected benefit obligation	4
Benefit obligation, balance, end of year	206	183
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	86	83
Actual return on plan assets	10	3
Company contributions	11	12
Benefits paid	(13)	(12)
Foreign currency exchange rate change, change in plan assets	4
Fair value of plan assets, balance, end of year	98	86
Funded status of plan at end of year	(108)	(97)
Postretirement Benefit Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	246	254
Plan amendments	(31)
Interest cost on benefit obligation, change in projected benefit obligation	11	13
Actuarial loss (gain)	12	(4)
Benefits paid	(16)	(17)
Benefit obligation, balance, end of year	222	246
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	19	20
Actual return on plan assets	1	1
Company contributions	14	15
Benefits paid	(16)	(17)
Fair value of plan assets, balance, end of year	18	19
Funded status of plan at end of year	$ (204)	$ (227)