Employee Postretirement Benefits (Pension Plan Assets of the Principal Plans Measured at fair value) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Fair value of plan assets	$ 4,840,000,000	$ 4,192,000,000
Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	362,000,000	1,024,000,000
Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	4,478,000,000	3,168,000,000
Cash and Cash Equivalents - Assets Held Directly [Member]
Fair value of plan assets	24,000,000	34,000,000
Cash and Cash Equivalents - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	24,000,000	34,000,000
Cash and Cash Equivalents - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	0	0
Cash and Cash Equivalents - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	180,000,000	99,000,000
Cash and Cash Equivalents - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	50,000,000	41,000,000
Cash and Cash Equivalents - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	130,000,000	58,000,000
U.S. Government and Municipals [Member] | Fixed Income - Assets Held Directly [Member]
Fair value of plan assets	187,000,000	174,000,000
U.S. Government and Municipals [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	93,000,000	123,000,000
U.S. Government and Municipals [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	94,000,000	51,000,000
U.S. Government and Municipals [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	472,000,000	52,000,000
U.S. Government and Municipals [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
U.S. Government and Municipals [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	472,000,000	52,000,000
U.S. Securitized Fixed Income [Member] | Fixed Income - Assets Held Directly [Member]
Fair value of plan assets	13,000,000	18,000,000
U.S. Securitized Fixed Income [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
U.S. Securitized Fixed Income [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	13,000,000	18,000,000
U.S. Corporate Debt [Member] | Fixed Income - Assets Held Directly [Member]
Fair value of plan assets	993,000,000	334,000,000
U.S. Corporate Debt [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
U.S. Corporate Debt [Member] | Fixed Income - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	993,000,000	334,000,000
U.S. Corporate Debt [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	185,000,000	199,000,000
U.S. Corporate Debt [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
U.S. Corporate Debt [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	185,000,000	199,000,000
International Bonds [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	765,000,000	619,000,000
International Bonds [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
International Bonds [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	765,000,000	619,000,000
Multi-Sector [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	2,000,000	57,000,000
Multi-Sector [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	2,000,000	1,000,000
Multi-Sector [Member] | Fixed Income - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	0	56,000,000
U.S. Equity [Member] | Equity - Assets Held Directly [Member]
Fair value of plan assets		615,000,000
U.S. Equity [Member] | Equity - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets		615,000,000
U.S. Equity [Member] | Equity - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets		0
U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	680,000,000	878,000,000
U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	3,000,000	3,000,000
U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	677,000,000	875,000,000
International Equity [Member] | Equity - Assets Held Directly [Member]
Fair value of plan assets	189,000,000	206,000,000
International Equity [Member] | Equity - Assets Held Directly [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	189,000,000	206,000,000
International Equity [Member] | Equity - Assets Held Directly [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	0	0
Non-U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	869,000,000	746,000,000
Non-U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	1,000,000	1,000,000
Non-U.S. Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	868,000,000	745,000,000
Global Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	252,000,000	217,000,000
Global Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
Global Equity [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	252,000,000	217,000,000
U.S. Equity Collars [Member] | Equity - Held Through Mutual and Pooled Funds [Member]
Fair value of plan assets	29,000,000	(56,000,000)
U.S. Equity Collars [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
U.S. Equity Collars [Member] | Equity - Held Through Mutual and Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	$ 29,000,000	$ (56,000,000)