Benefit Plans (Fair Values Of Pension Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	$ 6,167	$ 5,275
Registered Investment Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	178	187
U.S. And Foreign Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	20	46
Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	35	49
Other, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	25	31
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	1,212	753
Fair Value, Inputs, Level 1 [Member] | Registered Investment Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	128	124
Fair Value, Inputs, Level 1 [Member] | U.S. And Foreign Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	16	42
Fair Value, Inputs, Level 1 [Member] | Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Other, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	9	16
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	4,941	4,509
Fair Value, Inputs, Level 2 [Member] | Registered Investment Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	50	63
Fair Value, Inputs, Level 2 [Member] | U.S. And Foreign Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	4	4
Fair Value, Inputs, Level 2 [Member] | Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	35	49
Fair Value, Inputs, Level 2 [Member] | Other, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	2	2
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	14	13
Fair Value, Inputs, Level 3 [Member] | Registered Investment Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | U.S. And Foreign Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Other, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	14	13
U.S. Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	1,566	1,482
U.S. Large Cap [Member] | Fair Value, Inputs, Level 1 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Large Cap [Member] | Fair Value, Inputs, Level 2 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	1,566	1,482
U.S. Large Cap [Member] | Fair Value, Inputs, Level 3 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	499	441
U.S. Small Cap [Member] | Fair Value, Inputs, Level 1 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Small Cap [Member] | Fair Value, Inputs, Level 2 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	499	441
U.S. Small Cap [Member] | Fair Value, Inputs, Level 3 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
International Developed Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	179	152
International Developed Markets [Member] | Fair Value, Inputs, Level 1 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
International Developed Markets [Member] | Fair Value, Inputs, Level 2 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	179	152
International Developed Markets [Member] | Fair Value, Inputs, Level 3 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
International Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value		100
International Emerging Markets [Member] | Fair Value, Inputs, Level 1 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value		0
International Emerging Markets [Member] | Fair Value, Inputs, Level 2 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value		100
International Emerging Markets [Member] | Fair Value, Inputs, Level 3 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value		0
Long Duration Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	494	585
Long Duration Fixed Income [Member] | Fair Value, Inputs, Level 1 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Long Duration Fixed Income [Member] | Fair Value, Inputs, Level 2 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	494	585
Long Duration Fixed Income [Member] | Fair Value, Inputs, Level 3 [Member] | Common/Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Government And Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	625	510
U.S. Government And Agencies [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Government And Agencies [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	625	510
U.S. Government And Agencies [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	71	44
U.S. Municipal Bonds [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	71	44
U.S. Municipal Bonds [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Foreign Government And Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	311	204
Foreign Government And Agencies [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Foreign Government And Agencies [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	311	204
Foreign Government And Agencies [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. And Foreign Government Securities Or Their Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Above Investment Grade [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	714	618
Above Investment Grade [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Above Investment Grade [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	714	618
Above Investment Grade [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Below Investment Grade And No Rating [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	391	255
Below Investment Grade And No Rating [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
Below Investment Grade And No Rating [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	391	255
Below Investment Grade And No Rating [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	759	550
International Equities [Member] | Fair Value, Inputs, Level 1 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	759	550
International Equities [Member] | Fair Value, Inputs, Level 2 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
International Equities [Member] | Fair Value, Inputs, Level 3 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	300	21
U.S. Equities [Member] | Fair Value, Inputs, Level 1 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	300	21
U.S. Equities [Member] | Fair Value, Inputs, Level 2 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	0	0
U.S. Equities [Member] | Fair Value, Inputs, Level 3 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments at fair value	$ 0	$ 0