Retirement Plans (Fair Value Of Pension Plan Assets By Investment Category And The Corresponding Level Within The Fair Value Hierarchy) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Compensation And Retirement Disclosure Line Items
Total pension plan assets	$ 7,227		$ 6,250
Maximum equity holding percentage of total fair value	1.00%		1.00%
Equity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	3,791		2,719
Money Market Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	240		23
Fixed Income Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	165		176
Real Estate Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	32		28
Commodity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	8		8
Hedge Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	301
Insurance Deposit Agreements
Compensation And Retirement Disclosure Line Items
Total pension plan assets	108		107
U.S. Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	500	[1]	1,178	[1]
International Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	85		84
Private Equity Investments
Compensation And Retirement Disclosure Line Items
Total pension plan assets	8		8
Quoted Prices in Active Markets for Identical Assets (Level 1)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	1,072		1,760
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	303		224
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed Income Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Hedge Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Insurance Deposit Agreements
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	500	[1]	1,178	[1]
Quoted Prices in Active Markets for Identical Assets (Level 1) | International Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	85		84
Quoted Prices in Active Markets for Identical Assets (Level 1) | Private Equity Investments
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Other Observable Inputs (Level 2)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	5,907		4,347
Significant Other Observable Inputs (Level 2) | Equity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	3,488		2,495
Significant Other Observable Inputs (Level 2) | Money Market Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	240		23
Significant Other Observable Inputs (Level 2) | Fixed Income Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	165		176
Significant Other Observable Inputs (Level 2) | Real Estate Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Other Observable Inputs (Level 2) | Commodity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	8		8
Significant Other Observable Inputs (Level 2) | Hedge Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	201
Significant Other Observable Inputs (Level 2) | Insurance Deposit Agreements
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Other Observable Inputs (Level 2) | U.S. Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2) | International Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Other Observable Inputs (Level 2) | Private Equity Investments
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	248		143
Significant Unobservable Inputs (Level 3) | Equity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3) | Money Market Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3) | Fixed Income Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3) | Real Estate Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	32		28
Significant Unobservable Inputs (Level 3) | Commodity Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3) | Hedge Funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	100
Significant Unobservable Inputs (Level 3) | Insurance Deposit Agreements
Compensation And Retirement Disclosure Line Items
Total pension plan assets	108		107
Significant Unobservable Inputs (Level 3) | U.S. Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) | International Companies
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Significant Unobservable Inputs (Level 3) | Private Equity Investments
Compensation And Retirement Disclosure Line Items
Total pension plan assets	8		8
Cash
Compensation And Retirement Disclosure Line Items
Total pension plan assets	43		50
Cash | Quoted Prices in Active Markets for Identical Assets (Level 1)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	43		50
Cash | Significant Other Observable Inputs (Level 2)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Cash | Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Treasury Securities
Compensation And Retirement Disclosure Line Items
Total pension plan assets	141		224
Treasury Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	141		224
Treasury Securities | Significant Other Observable Inputs (Level 2)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Treasury Securities | Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0		0
Corporate Bonds
Compensation And Retirement Disclosure Line Items
Total pension plan assets	1,805	[2]	1,585	[3]
Corporate Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0	[2]	0	[3]
Corporate Bonds | Significant Other Observable Inputs (Level 2)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	1,805	[2]	1,585	[3]
Corporate Bonds | Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets	0	[2]	0	[3]
Asset-Backed Securities
Compensation And Retirement Disclosure Line Items
Total pension plan assets			60
Asset-Backed Securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Compensation And Retirement Disclosure Line Items
Total pension plan assets			0
Asset-Backed Securities | Significant Other Observable Inputs (Level 2)
Compensation And Retirement Disclosure Line Items
Total pension plan assets			60
Asset-Backed Securities | Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets			$ 0

[1] No single equity holding amounted to more than 1 percent of the total fair value.

[2] Our corporate bond investments had an average rating of BBB+.

[3] Our corporate bond investments had an average rating of A-.