Employee Retirement Benefits (Status of Pension and Other Postretirement Plans) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Pension Plans [Member]
Change in Projected Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 1,452,000,000		$ 1,257,000,000
Service cost	37,000,000		39,000,000		37,000,000
Interest cost	72,000,000		72,000,000		66,000,000
Plan participants' contributions	0		0
Net actuarial loss (gain)	198,000,000		131,000,000
Curtailment gain	0		(14,000,000)
Benefits paid	(35,000,000)		(33,000,000)
Projected benefit obligation at end of year	1,724,000,000		1,452,000,000		1,257,000,000
Change in Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	1,042,000,000		942,000,000
Actual return on plan assets	136,000,000		2,000,000
Employer contributions	84,000,000		131,000,000
Plan participants' contributions	0		0
Benefits paid	(35,000,000)		(33,000,000)
Fair value of plan assets at end of year	1,227,000,000		1,042,000,000		942,000,000
Funded status at end of year	(497,000,000)	[1]	(410,000,000)	[1]
Accumulated benefit obligation for our pension plans	1,600,000,000		1,300,000,000
Other Postretirement Plans [Member]
Change in Projected Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	183,000,000		180,000,000
Service cost	6,000,000		6,000,000		6,000,000
Interest cost	9,000,000		9,000,000		9,000,000
Plan participants' contributions	2,000,000		2,000,000
Net actuarial loss (gain)	9,000,000		(1,000,000)
Curtailment gain	0		(5,000,000)
Benefits paid	(8,000,000)		(8,000,000)
Projected benefit obligation at end of year	201,000,000		183,000,000		180,000,000
Change in Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0		0
Actual return on plan assets	0		0
Employer contributions	6,000,000		6,000,000
Plan participants' contributions	2,000,000		2,000,000
Benefits paid	(8,000,000)		(8,000,000)
Fair value of plan assets at end of year	0		0		0
Funded status at end of year	$ (201,000,000)	[1]	$ (183,000,000)	[1]

[1] Included in other liabilities of our consolidated balance sheets as of December 31, 2012 and 2011.