Employee Retirement Benefits (Qualified Pension Plan Assets by Asset Category at Their Fair Value) (Details) (Qualified Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 securities		Dec. 31, 2011 securities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	510		444
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	717		598
Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	1,227		1,042
Cash Equivalents [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	0		0
Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	16		22
Cash Equivalents [Member] | Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	16		22
U.S. Large-Cap [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	405	[1]	353	[1]
U.S. Large-Cap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	0	[1]	0	[1]
U.S. Large-Cap [Member] | Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	405	[1]	353	[1]
U.S. Mid/Small Cap [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	105	[2]	91	[2]
U.S. Mid/Small Cap [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	0	[2]	0	[2]
U.S. Mid/Small Cap [Member] | Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	105	[2]	91	[2]
International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of investments	6,100		6,400
International [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	0	[3]	0	[3]
International [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	215	[3]	167	[3]
International [Member] | Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	215	[3]	167	[3]
Investment Grade Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of investments	3,600		3,000
Investment Grade Credit [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	0	[4]	0	[4]
Investment Grade Credit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	486	[4]	409	[4]
Investment Grade Credit [Member] | Total [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets at fair value	486	[4]	409	[4]
International Investment Grade Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of fund assets	19.00%		20.00%
Minimum [Member] | International [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of countries in which investments involved	40
United Kingdom | International [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of fund assets	15.00%		16.00%

[1] Consists of a publicly traded equity index fund that tracks the S&P 500.

[2] Consists of a publicly traded equity index fund that tracks all regularly traded U.S. stocks except those in the S&P 500.

[3] Consists of an international equity fund that tracks an index of approximately 6,100 and 6,400 securities for 2012 and 2011, respectively, across over 40 countries. United Kingdom has the largest share with 15% and 16% in 2012 and 2011, respectively.

[4] Consists of a bond fund that tracks a broadly diversified investment grade index that consists of approximately 3,600 and 3,000 issuances of investment grade bonds for 2012 and 2011, respectively, from diverse industries. International markets represent 19% and 20% of the fund in 2012 and 2011, respectively.